Okay, I was in EXACTLY the same boat as you a few months ago. Lucky for you, you already have an air compressor. The NAPA down the street from where I work mixes custom paint cans and I thought "oh I'll just have 12 or so made up in horizontal blue and be done with it." You figure that is about 120 or so in rattle cans (usually they are 10 bucks or so, more if you only buy a few at a time).
My rational was that I wanted to take this truck out on the trail and there was no use in spending alot on a paintjob, and by alot I mean anything over 500 bucks. The guy at the paint store convinced me to buy a decent HVLP gun (100 bucks with contractors discount). At first I was just rattle canning the primer on and then I was going to shoot the enamel final coat with the gun. After about 20 bucks in rattle can primer I bought a quart of 2k primer and never looked back. When you rattle can, you have to put a lot of coats on becuase it goes on very thin. When you use the paint gun, you get a very nice coat, three coats later and your golden.
Here is my process:
1) Sanding and light body work (I had a majority of mine done last summer by next door neighbor, rust and a f'ed up fender)
2) Primer, sand, more primer more sanding
3) I used an acyrlic enamel or something, single stage, I didn't want to bother with a clear coat, mostly because this a truck, not a show car. Sprayed 3 coats, its a real bitch spraying the truck if your short and you a lift, that damn hood is tough to spray. Do at least three coats - see why on step 4. Also make sure its warm or your paint will run like its in a marathon, trust me I know. I chose to paint during one of coldest months in Seattle, bad idea.....being patient is important.
4) Let the paint cure for a few days, then wet with 1000, then 1500 then I used a couple diffent rubbing compounds. I didn't spray enough and then polished through the paint, so I had to do touch ups. In fact, I'm still doing them.
Here is a link to some pics
All in all, I think I spent around 400-500 bucks, not including the air compressor I bought, but I figured what the hell, I'll need eventually anyway. Any questions let me know, this was my experience, I'm sure there are some others on here who can tell you about their process. Do some searches on "rattle can", that may help you out as well.