Dulux 1 Step Prep is your first step toward a superior long lasting paint finish. With mould resistance and stain blocking of tannin and flash rust, Dulux 1 Step Prep ensures your interior or exterior paint shines now and into the future. Use Dulux 1 Step Prep for all general paint surfaces around your home including interior and exterior walls, ceilings, doors, windows, trim, and especially where mould is a problem including kitchens, bathrooms & outside areas.