How to cover stains and prime bare plaster with Zinsser Cover Stain - YouTube
HitlineUK Stain Blocker Spray Paint White 400ml, Damp Proof Paint Stain Stop, Seals in One Coat for Brick, Concrete, Cement and Plaster Walls, Damp Seal : Amazon.co.uk: DIY & Tools
Pro-Kleen Damp & Stain Block Spray Paint Primer White Matt 2 x 400ml - Covers Damp, Mould, Grease, Nicotine & Rust Stains - for Walls & Ceilings - Leaves a Waterproof Barrier :