I am painting my 96 ford ranger. I’ve been shooting Matrix brand primer/sealer over the areas that I have been doing body work on. I’ll be following that with urethane color and clear coat. My question is about surface prep on the portions of the truck where the body does not need any body work. My friend who used to paint professionally said I should sand off the existing factory clear coat down to the color coat before shooting on the prime/sealer. Is this really necessary or just extra work? Is scuff sanding enough? Although the clear coat is a bit dull, it is intact.