I am about to start sanding down a car I just bought. It has a horrible paint job. It is not the factory paint. However the original paint is black as well as the crappy paint on there now. I don't want to primer the whole car since I will be spraying it black. If I sand with 400 will it remove this crappy paint and get me down to my original black? Thanks
BTW I have searched the forum for this ? already.

 

crappy paint is a vague term to be using around here, your gona have to explain it further, is it physically damaged, or do you just dislike the color? Typically when repainting over existing paint you wet sand with 400 to scuff the existing clear coat, then spray a sealer, then your basecoat.

 

If you have a crappy finish, like its flaking off, your gonna want to get rid of all that crap. You dont want to try and shortcut it by feathering it out and saving time cause youll just have problems later on with whatever finish you put on it. knock it down with some heavier paper, get rid of the junk paint, prime it. Its well worth it to get rid of a crappy topcoat to ensure that your finish will stay and adhere properly.

 

when i refinished a used set of fenders, i used p80 on a DA sander to remove the old paint. (all FOUR prev paint jobs lol)

like IMPATIENT said, if you paint over the stuff thats falling off your car then whatever you paint over it will fall off. Id at least take the black color coats off sanding until i hit primer.

but dont listen to me im not a professional (:

 

The "crappy" paint isn't flaking off, it has runs, orange peel like crazy. I can wet sand with 400 down to the primer but it will quickly go through the primer. If I'm gentle with 400 I won't go down to the primer but I can't tell which coat of black I am in. I experimeinted on a fender I will be replacing.