What is the best paint stain blocker?

The best paint stain blocker often depends on the specific stains you're dealing with, but products like Zinsser BIN and KILZ Premium are highly recommended. Zinsser BIN is a shellac-based primer that effectively blocks tough stains, including water and smoke damage, while KILZ Premium offers Excellent adhesion and mildew resistance for a wide range of surfaces. Both options provide a solid base for paint and help ensure a smooth, clean finish. Always choose a product suited to your specific needs for the best results.