Thought about this after I posted last night, and figured I could have added more, so....
Your going to want to practice first. Just get a piece of sheet metal and spray it out. When spraying, there is a fine line between dry spray, good, and flooding/runners. You don't want dry spray or flooding. When spraying, you want a wet even coat. If its humid outside, avoid painting. Your atomizing the paint when it leaves the gun, if its humid out, the paint will pick up the moisture in the air, and can cause blushing of the paint. This will create a fog look in the paint, and without being able to heat the panel you may have to re paint it again.
I don't know what your budget is, but if you need a gun, get at least a decent priced one. A buddy of mine had a cheap one, and I just plain didn't like it. I'm not saying to buy you need a bad ass Sata, but a devilbiss is a nice mid priced gun that sprays well. I use a Devilbiss JGA, but they have other guns also. You will also need different tips to spray the primer and paint to make it flow correctly. I have sprayed with the same tip, and yes its possible but, the correct sized tip makes it easier. When you get done spraying, clean the gun, everytime you get done. For example, first session of primer, clean gun. Next session, clean gun. Keep it clean, and clean it right when you get done. Take the gun apart to clean it, piece by piece. Use lacquer thinner to clean it since lacquer thinner is cheaper than enamel reducer and the special gun cleaner. Use a air line water seperator/dryer in the line heading to the spray gun. You don't want wet air atomizing your paint.
This is currently what I have been using for projects, and I like it.
Nason SelectPrime 2K Urethane Primer
Nason Selectseal Urethane Sealer
Dupont Chromabase Paint
Dupont Chromaclear Clearcoat
For coats,
Priming
2 coats,then Sand. Then a coat(judging by how good it looks after one coat, if not, 2) then sand. If you only sprayed one coat the last time, you probably don't need to spray primer again, if you did need 2 coats, then you may need to prime it again, in this case, just one coat.Then sand,
Sealer
1 coat
Paint
3 coats
Clear
3 coats
Too much clear can crack, and fixing it isn't pretty.
Nason is a "budget line" of Dupont. For priming and sealing, it worked well for me. If you have bare metal spots, your going to want to use an etching primer on it first. Dupont or Nason(I forget) sells an aerosol can of it and it allows you to just spray the bare metal first, then spray over it with the 2K. It will be a 1K etch primer, it needs no activation, just shake the can and spray. Try to only use aerosol for small little bare metal spots. Use the activators and reducers designed to go with the product you are using. Don't use Valspar activator with Dupont products, Sherwin with Valspar etc. I would also avoid high pearl and high metallic paint since its your first time. Using them makes mottling(strips, bloths of metallic) way easier to do. Overlap according to the directions given by the supplier. With anything you buy, ask for the Material Data Sheet. Its basically all the information you will need to use the product. Air pressure, flash times, overlap etc etc.
If I think of any more tips, I'll post them up. If you have any questions post them up!