Before painting your walls, make sure that they are clean, smooth and completely dry. Stick down any loose wallpaper before washing the walls with a mild detergent, rinse with clean water and let them dry thoroughly.
Depending on your surface, you may need to use an undercoat. If you are painting onto vinyl wallpaper, you will need a coat of Multi-Surface Primer to create a base for the paint to sit on. If you are painting over a strong colour, Crown Basecoat will prevent it from showing through the finished job.
Use a 2 inch brush to cut in at the edges. Use the brush on edge, working in long sweeping movements across door frames and skirting boards etc.
Finish the job with a roller and tray, dampen the roller to make it easier for it to pick up the paint. Start in one corner and work across the wall in sections. Work the roller in a W motion and fill in the spaces as you go, as demonstrated in the video below.