Go to a good auto paint and supply store and they should have the rattle cans of paint you need. Made specifically for plastic.(Where I got mine butt.....the name of the paint slips my mind.)
I painted a junkyard console and bucket seat trim from an Oldsmobile to go in my S-10 FoMoCo parts chaser. The parts were gray and I changed the color to Maroon. Its been 3 -4 years and still looks great. Zero chipping..scratching..fading. Maybe the trick is cleaning REALLY well with lacquer thinner/Brakleen(I love that stuff) and several coats of paint...let each coat dry before re-applying. I even re-painted the padded dash and window's plastic trim as well as seat belt trim.
Looks great.
I have "heard" dye works really well on fabric/leather seats too.
6s6

I have had good success with several plastic paints/coatings but as usual preparation is everything. If the car was ever owned by a smoker, it is much more difficult to get clean enough for best results. Like most other painting projects, the more disassembly you do the better. I have had good results using alcohol for final wipe down. Make sure you test all your cleaners in a hidden spot.

SEM is the way to go for what you're  looking to accomplish on your fox body mustang.  They have adhesion promoter, plastic primer Which you could have tinted so that if the top coat gets scratched off you don't see an I sore color underneath.  One thing people done realize they are supposed to use to prep plastics is well the obvious " plastic prep". The closest thing I can describe plastic prep to is a Lil finer fast orange hand cleaner.  They pumice in the cleaner scuffs and promotes a superior bonding surface.  A lot of paint shops will also use this and prep steel panels with it. This scuffs the panels about the same amount as a new gray scuff pad.  Me I've used the plastic prep with great success. But one trick for when you're working on prepping textured interior panels or textured cladding panels on cars, I use plastic prep but in conjunction with a 3m green heavy medium or heavy scuff pad. The scuff pads are available at Lowes. I don't care for the cheaper off brand ones at Homedepot. Hope this helps.  Oh by the way if any plastic parts are broken in the car now would be the time to invest in a plastic welder. They aren't to much money, some even come with welding rods to help you get started.  Lots of 80-90s ford and gm use ABS,PVC, PP (poly propylene). Plastic panels on the cars and trucks. Do to regulations  plastic manufacturers were told they have to mark every piece of plastic  with an ISO Code.  This code tells you what type of plastic that piece is or you can do a stick test.  Melt a rod on the plastic and if it sticks there you go.

That's exactly what you should use. Like I said use plastic prep pumice cleaner use the scotch Brite and in not to long you'll have an all new fox body. My buddy who is an upholstery guy he uses SEM interior coatings as well. I'm in a body shop I'm actually not the head painter. I use the sem cladding paint seam sealer Epoxy many many things and I've been satisfied with them all.

Thanks for the advice,
I love this car even though I hate the interior, the body is extremely straight, and zero rust or previous paint work. I know interior work while not necessarily cheep is easier than body work.