tips on interior painting??

I suppose you're refering to a 74 Valiant ? Pictures would help.
Everything you can take out of the car should be painted out of the car.
About those plastic clips in the seals... Some will break while others tair the rubber. Just cut them. They can be replaced.
Nothing inside was painted a high gloss. You can but you wont like it. It will show every finger print. The dash paint is a flat low texture they called suede finish. I dont have a clue why you asked about the rear window.