Sounds like you used a scrubbing pad not meant for glass -- there are some that are glass-safe (they're usually white or blue). You'll need to get a glass polish -- Eastwood sells a couple of kits (
http://eastwoodco.com/, and your local auto parts store might have one that includes cerium oxide -- about the only thing that will fix that.
Mudflap gunk could probably be cleaned up with some mineral spirits or WD-40. Wax afterwards.
Overspray can often be removed with a good clay bar (I like Mothers Clay Bar), but it's tough to say how difficult it would be on the surface you're talking about. If it's indeed overspray, or simply waxy buildup in the textured plastic. If it's wax (and even if it's not), try Mothers Back-to-Black and let it penetrate... might take a couple of applications over a few weeks. Lightly buff to a soft sheen after each application.
Your Woolite mix should be fine for interior cleaning if it works for you. There are over-the-counter interior cleaners... milder is better and if Woolite works good most of the time, then use the dedicated cleaner only when you have to.
Leather conditioners won't restore damaged leather, or leather that has a "patina." It doesn't take much wear to give Mustang leather a leather patina. Again, I use Mothers Leather Cleaner and Leather Conditioner, but it may not make a significant improvement at this point. Anything you use will require periodic re-application. Apply when the surface is clean and cool, and well-vacuumed along the seams. If you have excessive soil, use the cleaner first. Generally you'll want to apply the products to a microfiber cloth or applicator for better distribution. Buff lightly with a quality cotton terry towel when done.
Sounds like you might cruise online for resources like
http://detailguide.com
Lot's of Q's.....
