Before I made any decisions, get a price from the powdercoater. When you add up the cost of the re-blast, paint , thinners, shipping, etc, it may be cheaper to let the powdercoater guy do all the work.
As for the air compressor and the spray gun, if you are doing a frame off restoration, you have a lot of painting and priming to do before the job is complete. Even if you send the exterior body parts out for a professional job, you still have all the engine, tranny, rear end, brake backing plates, etc, to prime and paint. You will need the spray set up eventually..
Before I started on my 53 I had no experience with a gun. With a little practice on parts that never see the light of day ( frame parts for example ) I now find that the gun is easier to use and does a far nicer job than a rattle can..
There is my .02 Jeff, Good Luck..