Primer Questions

I always use a transparent sealer like Diamont DS30 or its equivalent or a tintable sealer. It adds adhesion promotion, helps fill sand scratches, and if you're shooting a color that is prone to taking 37 coats to hide, then the tintable helps out on the BC usage. While it's not what I do to earn a paycheck now, I was certified for PPG, Diamont/Glasurit, and Martin Senour paint lines. While I agree that you don't need to use a transparent sealer, I've never had it be detrimental to a paint job.