So I wrote this as part of a response to something else. Then I figured I should repeat paste it as a guide itself.
In particular, Pyros are underused for how they should be used. Fire Shield ability is not used incredibly often despite being a main feature of the role. If you think you know where this is going, you might not need to continue.
Blue Flame (X Type) kills (or tries to). Use this to really put the hurt on. Just be careful. It can really hurt marines. 40 dmg a second. Very useful against T1s. Useful against T2s.
Green Flame (B Type) clears. This can be arguably more important but you ain’t getting kills. If you use Green Flame + Fire Shield you can “walk” your flames up a advance. Watch the timing - this takes experience. Your armor provides a buff when talking about burn damage But rule of thumb: Don’t go in fire without Fire Shield. Add in your extinguishers (inbuilt or otherwise) and you can secure ground and most xenos can only watch. 15 dmg a second so poor damage, but it slows and is just generally annoying (xenos don’t like catching on fire and it wastes their time to have to fallback and quickly roll).
Normal Flame: Generally, don’t bother with. It’s utility (for Pyro) is that it dissipates faster than Green Flame and does semi-decent damage. Also dumb easy to get so it’s useful to clear weed nodes when outside of combat and you don’t want/need to use Green. In combat however, Blue kills way better and Green clears (and gets xenos to back off) way better.
- Mag Harn your flamer.
- Get a Secondary Main Weapon (unlike other specs, you can even mag harn your second gun without fear of losing your flamer because the Pyro Flamer automatically will drop into your Pyro Backpack). Shotgun or Rifle for example.
- Get some spare ammo for your Secondary.
- Get a spare canister or three of Special Flamer Fuel for your Flamer (Type B or Type X. Don’t bother with normal stuff. One Special Flamer Fuel is like 3-4k points last I checked. Req won’t be amused to learn you need three new canisters in a long round because you spent it all on AP M4A3 or something kind of dumb.
- Get the rest of what you want (attachments for the Secondary, nades, webbing type, pouch type etc).
- Recommended you pack Ointment.
- Helmet Dump: You do not need use the Pyro helmet to use the Fire Shield. Also, Pyro helmet is more obvious than the normal one so you might get targeted more. Personally - do what you want. A Pyro is pretty obvious due to weapon, ammunition usage, and Fire Shield usage. The more you try to disguise yourself by dumping signature Pyro stuff (like Type X, Type B flame usage or your pyro backpack or pyro armor) the less effective you become.
- Revolver Pistol Loadout: Revolver for heavy ammo stun plays if you have good key binds/macros, VP78 if you want some extra damage, belt slot generalbelt: large extinguisher, + one extra fuel tank or MD, Etc
- MK1 Pyro Loadout: Can mag harn the Mk1 and Flamer, carry 3-4 spare MK1 mags in your armor, put nades/medical stuff in black/brown webbing, MD in belt, spare canisters in flamer pouch, and carry a sling harness for binocs to determine where marines need you.
Example of a Pyro Push
(using Lv-624 while pushing North from Containers into the Caves)
- Understand the situation: Are there Ravs? Queen? Are there Warriors? Is there a Boiler? Are Marines pushing or just shooting down the corridor uselessly? After factoring the issues: Choose to Push or Not.
- A Queen: Don’t bother even Pushing. This can and will single you out to kill you. Pyro Specs can absolute destroy marine pushes by accident but they can also destroy xeno pushes and single handily push entire fronts up on their own if they are moderately successful in any variation of a Pyro Push. GIBBING is expected in the same way a semi-successful Grenadier or Demo can expect gibbing. Pyros might not have the same killing power as a Demo, for example, but they are incredibly noticeable when they are active often.
- A Rav: Extreme Caution. These can stop your attempt in its tracks. Sometimes better to not even attempt with one around.
- A Warrior: Don’t stray to the edge of your flames closest to the xenos when you do this manuever and watch what the warrior does - Some warriors will take the risk and try to grab you while you are flaming so you have to understand their possible intent.
- Boiler: Caution. Sometimes the process works so well you can set one on fire and other times a convenient blob forces you to fallback before you really began.
- You’ve chosen to push! Fire Green Flame north. Listen to marines rage about stopping the non-existent push (optional).
- Activate Fire Shield.
- Run into the fire. Keeping in mind the possible threats (Ravs, Queens, Warriors, Boilers, on fire Lurkers pushing you etc), run north in the fire and fire Green Flame further north. Avoid exiting the fire on the xeno side of the push when doing this manuever. It’s just not worth it usually.
- Run back to the Marine side of the push before your Fire Shield runs out, which is now separated by Green Flame from the Xenos’ side, and use your fire extinguisher on the flames closest to the marines.
- Desired Effect: The Marines have a net gain of ground and you gain ground. You have just successfully “walked” the push forward, via Type B Flames, Fire Shield, and Extinguishers. Repeat until marines are able to push without you.
Other stuff to consider:
- Avoid blocking pushes with flames
- Understand the difference between marines shooting down a corridor and dancing in front of xenos and a push.
- Use your Extinguishers. You even get on attached to your Flamer. It has a lot of water. Don’t be stingy.
- Do not worry about conserving fuel. It will take you quite a bit to exhaust all your fuel (or even one canister). Normal fuel is dumb easy to get. Special fuel harder (since it requires req or you to have bought spares) but it is not as demanding on Req compared to Demo or Grenadier resupplies.
- In large, desperate retreats don’t be conservative with fuel. Try to be the last man in the group/behind everyone and flame flame flame behind you. It will slow down most xenos and force even Ravs and the Queen to consider their odds in fighting without most of the hive. This advice goes for normal flamer usage too by the way.
*Something I enjoy doing is shooting Type B through open xeno doors. The door closes. But the fire remains. On occasion this gives time to shoot or clear the doors (sometimes even on your own).
The Bane of the Pyro?
The most common things I’ve seen that will get you perma’d when using concepts found in this guide
- Assorted Friendly Fire.
*Edited to add some stuff based on comments.