I just painted my -4 using Valspar (same paint Van's uses). I used their epoxy primer in white and their polyurathane paint. Mostly I used a Harbor Freight 2Qt pot HVLP gun and an Alltrade gravity gun for the color. It required a little over a gallon of primer and about a gallon and a half of white pluss the activator & reducer etc. Took maybe about 12 oz of red and maybe 16 oz of blue. Total cost for materials (paint, activator, reducer, clean up, mask, suite, measuring containers, strainers, masking supplies, dryers etc. etc. about $1000. Another $150 to build a booth out of PVC pipe and visqueen.
As a side benifit I later found out that a lot of farmers use this same epoxy primer on the inside of their chemical tanks. Must be pretty tuff stuff. For my base color I used fleet white and therefore was able to return what I didn't use (full can). I am very pleased with the results once I learned how to set up and use the gun. Used about 35 to 40 lbs pressure at the hose and set the pot to about 7 lbs. The pot sprayer allows you to spray longer and in any position. I used the gravity gun for the color only because I had it and it is a little easier to clean up. The HVLP seems a bit harder to get a smooth coat, but once you get it set up right then it work great. If you run too much pressure to the pot it's easy to get orange peel.
I can't say enough about lights. When you think you have enough, double it. Even then, have someone (with proper protection) hold additional lighting so you can see the reflection of what you are doing.
I say if you have a place to do it and don't have a reasonably priced & dependable painter person, do it yourself. It's a lot of work but worth it.
I had mine at a shop for about 4 months and the guy only wanted money but did very little. Finally had to fire him and hire the most dependable person I know - me.
This is in no way a condemnation against any other paint brand. I am in no way an expert on the different paints available. I settled on Valspar for several reasons. Van's uses it, It's available nearby, and it seems to be a very good product. Also, it's fairly easy to use and the supplier was very helpful.
Good luck