Most of the time I have started my projects with unpainted bodies, so stripping of paint was not an issue. In one case I started with a car that had tampo printing and I just shot that with two light coats of model spray primer. Since the printing did not show through I sprayed over the primer with regular model paint, automotive paint also works well. Model paint is not very durable and if you put decals on the car they are also easily damaged. It is best to coat everything with a durable finish, I use an automotive clear coat. The clear that I use can attack decals, so I protect those with a couple of coats of Future. Future is water based and if you brush it on inkjet printed decals they will smudge. For inkjet decals you can use an acrylic spray clear coat before you cut out the decals and put them on the car. You do have to be very careful what sort of paint you put on bare plastic. Paint made for model car bodies should not attack the plastic. Once you protect the body with a primer you can use many kinds of paint over that, but it is best to do some test sprays on something that is expendable.