Carlos,
I almost always use automotive acrylic on my car models - it dries very fast, and can be polished to a mirror finish using ordinary car polishes.
I've always had perfect results - you just have to be a little careful, that's all.
Always use a spray booth or spray outside - the fumes are awful to breathe. If you plan on using the automotive two-pack (I can't imagine why you would) use an approved respirator capable of coping with the nasty fumes - they're seriously bad for you - check with your local government OHS officer for the correct type, or call a spray painter.
I always thin the paint pretty heavily so it goes on very thin - if I'm spraying lighter colors, including reds, yellows, whites or blues, I tend to use white as a primer, as this allows for a richer, fuller color saturation without having to apply 20 color coats. But for darker colors and blacks I just use gray primer.
Again, I try to thin the paint as much as needed to get a really thin dust coat for the first few coats of primer, then do the same for the first few coats of top coat.
Then, hit it with a wet coat (after allowing sufficient drying time between all primer coats and color coats to prevent crazing or warping) and then another one. I find this usually is all that's needed.
Remember, the thinners and the paint are "hot" and will attack sytrene if applied too thickly.
It always pays to experiment on a scrap car model to get the feel of the paint - I've even gone to the trouble of purchasing a really cheap model just to get a body to practise on.
Remember, patience is the key to all success in modelling. If you're patient, you can figure things out and will have far fewer disasters.
Take my word for it. It's taken decades for me figure this one out.
Cheers,
LeeTree