I will be detailing a older car (Buick) for my mom-in-law for mother's day. I was wondering if it was worth claying before using polish on the paint to clean it up. The paint is in fair condition with some oxidation. I will be using 1Z polishes. I bought all 3. I'm thinking of starting with the Ultra polish. But is there any use claying this car first or is it a waste of time on a older car that hasn't been detailed very often. Thanks for the advice, Wes.