Get the ultimate hiding power indoors and out with the Zinsser Cover Stain oil-based primer. This whole-house primer-sealer is a favorite with professionals. Use this primer to block stains, hide dark colors, prevent tannin bleed, and penetrate and seal exterior wood. Paint Sub-Category: Oil-Based; Primer; Spray Paints; Specialty; Intended Application Environment: Interior/Exterior; Finish/Sheen: Flat; Color(s): White.