Spray painting really is not difficult, actually when i did my camaro hood it was the easiest part of the job. I setup my spray gun and first coat i spread was on the hood without any practice ever and it turned great. (its probably best to practice before)
I used the devilbiss finishline many people say they are the best bang for the buck and if you want better you have to pay alot more.
Hvlp is better but make sure your compressor is big enough if you want to spraypaint the car all at once.
If you have to use waterborne paint(personnal choice or local law/availability) make sure the spray gun you get is compatible!
As chrome bumper said, most paint can be fixed with some color sand and buffing.
Single stage metallic cannot be sanded/buffed, this mess the metallic.
Your probably going the basecoeat/clearcoat route for a better and more durable paint.
This can be fixed so long you dont get runs in the base coat if using metallic.
Its pretty simple, if you have metallic you cannot sand, but if you have a clearcoat over it you can buff/sand the clear.
I use a air valve with a pressure gauge right at the spray gun air input, this way am sure i have the correct pressure if using long air hose/normal quality fittings and also allow me to set it right at the gun.
Use a good water separator at the compressor and also air filter at the spray gun.
something like this at the spray gun:
Long copper tubing between the water separator and compressor increase the water separator efficiency.
Setting the spray gun is pretty easy, i think the link Grumpy posted may cover it, or google/youtube has great info but am still going to share the little i know.
I like to be about 8-9 inch away from the surface with about a 8-9 inch spray fan width.
Always re-check/re-set the pressure at the gun after you changed the fan width(changing fan width change your pressure).
And there is the setting for the needle/material, i usually spray for 1 second without moving(on the same spot) and adjusting so its not running (too much material)and it do not have poor coverage(not enough material).
Since your going metallic, you may search about orientation/drop coat, its pretty simple.
The flash time and time between basecoat clearcoat, all this info usually its on the instruction from your paint system and clearcoat product.
Oh, and buy a quality paint and clear coat
BASF and PPG are what people are using here for paint.(i did use BASF Onyx HD)
Try to make a good spray booth(i used furnace filter), if you can get a good result without color sanding and buffing, your saving time.
If your working outside you can wet the floor, and i like to let the an run for about 15 min before i start painting, this remove dirt in the air.(i used square box fan)
For a quality spray booth people use the fan to pull the air out, if using a cheap spray booth like i did, its probably best to set the fan to push the air in instead.
edit
h and do 50/50 overlap when spray painting.