.Insl-X Reduced Odor White Flat Oil-Based Alkyd Primer 1 qt This stain-blocking primer dries to the touch in 30 minutes and is effective at sealing water stains tannin soot and smoke stains on fire-damaged walls nicotine stains rust stains and more. It can also be used on exterior masonry and to spot prime exterior wood shingles and composition siding.