Plus, with as expensive as paint is these days, I'd hate to throw that money away.
VALID POINT.
A major part of having positive results is proper preparation, but
the real magic is in knowing the science behind the paint, proper thinning/mixing, having a good gun/compressor and knowing your equipment. Granted, practice is key in getting good. My friend Bobby Gilyeat swears by starting with cheap paint and a couple old car hoods until your acquainted with your gear.
Don't try to jump in with something fancy where you have to add pearl or metal flake, weighing stuff by milligrams, ect.
It takes a while to master mixing AND doing so in such a way you'll be able to duplicate it at a later date. It's best if you can find someone who doesn't mind mentoring you. But even if you do, don't be surprised if they
don't share EVERYTHING with you. Some masters hold their secrets like it's a Holy Grail. (especially if you are wanting them to duplicate an antique color)
I've been an artist since a young child (tempera, oils, acrylic, charcoal, soft lead, and ink/inkwash are my favorites) but working with simple rattle cans can bring about amazing results if you've prepped your piece and have a draft/dust free working area with excellent lighting.
BTW, lighting from at least three different directions is paramount.
I just think there is something very special about the medium of paint that allows you to express yourself.