Whatever you use:

would pick a store close to you, so you can get anything you need right away, and have some solid information about that paint system.

I would use their first line paint. Second line paints will either fade sooner, or start losing their gloss sooner. If it's your own stuff, you will want it to look good five years from now, instead of having to repaint. If it's for a customer, he will never come back if the paintjob fails quickly.

Pick a company that can mix all production colors. Companies like HOK and X-Otic make good products, but what if you like a color you've seen on a new car?...or you want to fix a friend's car? ....or you want a bunch of colors to choose from?

Once you choose a system, you will want to stick with it. It always takes a while to figure out how to get it to work every time for you.

You might befriend a local experienced painter who does the kind of work you want to do. He can be a resource to help you solve or overcome problems.....and we all have them occasionally, no matter how long you do this.

Good luck!