I cut the finishes with mineral spirits. This allows the "sealer" to penetrate the wood. I usually "soak in" three coats of sealer prior to using the final un-cut finish. And if I am staining, I mix the stain with the sealer.

"Soak In": Brush on a good heavy coat, when it is almost dry, brush on another, repeat until I have the number of coats desired. Let the final coat dry a few days prior to finishing.