HVLP stands for high volume low pressure. And they use compressors. As for the 2 part paint, that is what is known as catalyzed enamel, and it is very dangerous to use. You have to have the proper safety equipment, and even then it is hard to get it right. It takes a lot of skill and experience. It's also super expensive. HOK (House of Kolor) is probably the most common brand, and they sell paint that can cost up to several hundred $$$ a qt. For a frame, if you are willing to completely disassemble the bike, and strip off all the old paint, the best method for refinishing it would be to have it powder coated. I had a set of car wheels powder coated and they came out beautiful. That was 10 years ago, and they still look great even after sitting outside in the AZ sun.
As for tanks and fenders, Eastwood makes a clearcoat in a spray can that is supposed to make any paint gasproof. I have had excellent results with acrylic lacquer, like DupliColor and PlastiKote, but it is definitely NOT gas proof. Even WD-40 will mess it up.