On the surface it may seem like $300 for "a pro" to do the paint job is a bit much. So you want to do it yourself? If you are only considering this (one) paint job, you'd be better off farming it out.
You have a compressor already, but that's just a start. You need some type of filter system and water trap and pressure regulation. Guns? It depends. For a one time job there are some decent $40 guns, but you need to have the experience to get the most out of them. However, the same applies to a top line gun. One can easily spend upwards of $300-400 paint gun. But you gotta know how to use it. The "pro" has, and most likely does.
Materials? Modern materials are expensive and one could easily spend $150-200 in materials just to paint one frame. The biggest problem is the minimum order requirement. And, without experience in the application of these materials, you could waste the whole batch. What if things go well? What are you gonna do with the leftovers?
Frame prep? It's key to a good paint job. It also requires some skill and knowledge- not to mention a little bit of equipment.
I don't mean to scare you off, but to gear up to do the type of paint job the pros deliver is ouitside the capabilties, and budget of a beginning painter.
"flake off in three years?" Hard to quantify that one. You will not find a guarantee on any paint job that covers three years.
Solution? Powder coat is one. Another is give it a go yourself.