lol long time since I used them brushes ;-) ....if the same ones I have is about 10 images so could make an animated brush, if only one image then try using warp(liquefy) suggesting the paint way as a stress-free quicker way then a smoke sim

in blender load a plane (anything) then go to object on bottom menu an pick quick effects/smoke.........that will automatically load a domain and set smoke.stuff then hit play on timeline .........you will get a nice "nuclear" mushroom of thick smoke.......now its time to look at the settings ....is lots blender guru has some good tuts on smoke but is lots on youtube too once you got it lookin ok then you need to bake it (you need to save file BEFORE baking but good idea anyway just in case blender crashes ) hope that helps