I have tried propane tanks, butane and heat guns. They each have their slight differences but all can be used.
Propane: I like propane torches because the cylinder is larger than a butane torch and it lasts quite a while. You can purchase a nozzle that allows you to control the flame and also lock the flame in the "on" position which is very convenient. I also use a propane tank (like those you see on camper trailers) with a hose and nozzle - it is lighter to handle just the nozzle rather than lift up the more portable propane torch - but that is for some really serious encaustic work! Propane torches are a bit heavier and have a bigger flame so if you are not comfortable using a flame, you may wish to start with a smaller butane torch.
Butane Torch: There are many brands of butane torches - many are used by chefs. The one I use is the RAVS butane torch and it is fairly simple, which I like. It has a dial which allows you to control how big the flame is - which is a great feature. I once bought a chef's torch and there were too many functions that I found confusing. Though the listing may say this torch does not use the "Zippo" brand of butane fluid, or any other brand, it has nothing to do with the fuel itself, but rather the nozzle which fits on the bottom of the torch. I have not personally had any difficulty filling this RAVS torch with the Zippo brand of butane fuel; I'm not sure why thy say it doesn't work since it does work just fine!
Heat gun: A heat gun works just fine to "fuse in" your encaustic layers. There is no open flame, but rather it usually has two levels of very hot heat - much, much hotter than a hair dryer (please do not use a hair dryer; it will not work to fuse in the encaustic layers). Here is the one I use: https://amzn.to/3ke46TS
