IMO, you can restore anything. The rougher they are, the more primer you will need. Honestly, I didn't sand much on a bad pair I had. I just hit them with 80 grit to loosen the cracked areas. Blow them off real good and go to town with the primer. Spray bomb primer will take forever. I literally used 2 or 3 cans on a pair one time and they still weren't perfect. I highly recommend Nason 2K Urethane primer. It's activated and you mix it 4:1. You can even thin it out with a little bit of laquer thinner. I do it all the time, but to get it to spray easier cause it's so thick.
I would spray 2 wet coats (wait 15 minutes between each coat @ 70* temp...longer at colder temp). I would let that dry at least 3-4 hours @ 70*...longer if colder. You most likely will still see holes/divets. Simply sand them down with 150...blow off...spray again...2 more coats. Usually...4 is a done deal. Sand them with like 320, then 400 or 600 spray them with your black paint/clear. Done deal. If they still have imperections...get more coats of primer.