Like anything, it takes practice. I've used spray paint on two helmets and a few repaints. Most paints work well, but one of the paints (I'll have to look) has a tendency to crinkle if sprayed on other than a very light coat. Remember, if you don't like it, sand it and paint again!
the crinkling is caused by a chemical reaction between paints. if you are unsure of whether there will be a reaction in the paints you are using, test it on some scrap. i learned that the hard way.
also, use Rogue Studios color list(use the search function luke!). most of the floquils come in spray can form and can be ordered from testors.com. i have heard of people on here using brushes and getting good results. perhaps some of them will chime in.