How can I take out a Heavy using the Huo-Long Heater?

Solution 1:

To avoid getting burned by the Heavy's Huo Long Heater, instead of charging towards his back, try jumpstabbing from higher positions. Hold crouch while positioning yourself on top of him, then stab when you land on him (remember to hold Crouch).

Trying to run to his back and stabbing him will set you on fire, even whilst the Heavy dies. So for these guys, I typically try jumpstabbing.

If you care less about getting burned, and more about making kills, use any knife besides the Spycicle. The Spycicle will be consumed when hit with fire, rendering your one-hit kill backstab gone, so take care when choosing the proper knife for the job.

If you care more about your life than making picks, then go with the Spycicle. At the very most, if you attempt to bypass that half-second delay of flames from the Huolong, and mess up, you can still get away without getting burned.

Solution 2:

One technique is to activate the Dead Ringer after a successful stab. You will be set on fire briefly (taking slight damage), but the Dead Ringer's effect will extinguish the flames.

It's very important that you activate the Dead Ringer after stabbing the Heavy (or at least after retreating if you feel your cover is blown) or you will be set on fire while cloaked. Not only does this reveal your location to enemies, the fire will also drain your cloak time, leaving you very vulnerable.