plasticote engine paint is crap

I always soak my fizz cans in the sink with the water on hot for a few min then shake really well and warm some more then shake and spray. (can shout be warm in the hand) I use to have problems with the dupi color stuff until I figured out the secret (prep, prep, prep, primer 2x coats, color 2x coats clear 2x coats, let flash for 10 min between each coat, then after and hour or so of dry time take the propane torch to it and make the clear glossy) and now I can't get that stuff off if I try.