Gel coat is nothing more than colored resin, and resin has styrene in it. The use of acetone will make the gel softer, and will scratch very easy. You will have to spend a little bit of time finding a good gun, most have a tip that is no good, to small. 2.0-2.5, I don't go any smaller than 2.5, I also use a 2.5 gallon presure pot. I save empty water and or gallon mik jugs, cut the top off and leave the handle. I will mix the gel and catylist in the jug and set it inside the pot, and I do the same thing with the acetone, clean up is super simple, the pot never gets dirty and only takes about 1/2 gallon of tone to clean the lines out.