As I get older, (and lazier), I was thinking of having two cannons ready to go. One with Griots Surface wash and the other with Griots PolyGloss. Rather than having to stop, unscrew the head, screw it on a rinse bottle, rinse it, unscrew it and put it on the PolyGloss bottle, unscrew it, put it...
I've had success using Nextzett Plastic Deep Cleaner to remove wax from textured plastic. Should work on smooth, too.
Mike, have you ever used the Solution Finish on grey trim?
I used Jescar Tire and Trim. It's supposed to have a "Satin" finish. I find it a bit too glossy for me.
My go-to has been Nextzett Vinyl Rubber Extra. I love the looks, but it doesn't last.