To get the best results from your painting efforts, professionals recommend a thorough sanding before painting. This advice applies to most projects, whether you're painting a wall, piece of furniture or wood trim. Sanding serves several purposes: it removes layers of chipped, flaking paint, and it removes gloss, resulting in better paint adhesion. Sanding also removes rough texture, dents and dings, resulting in a smoother finished surface. Sanding is not difficult, but can become tedious and tiresome, especially if you are working on a large area. An electric sander is not required but makes larger jobs go more quickly and easily.
Put on your dust mask and safety goggles.
Choose a sandpaper based on the item you are sanding. If you are sanding to remove old layers of chipped paint, a larger grit --- designated by numbers 40 through 60 -- will work best. An item with smaller imperfections calls for medium grit, designated by numbers 80 through 120. Use fine grit, numbers 150 through 180, for a final sanding before you begin painting. When sanding, always start with the coarsest grit appropriate for your piece and move up incrementally to the finest grit.
Attach sand paper to your sanding block, electric sander or other sanding tool per the manufacturer's instructions. You may also simply hold the sandpaper in your hand. While larger electric sanders make quick work of larger areas, small detail sanders are also available in both manual and electric models. Detail sanders are helpful for sanding odd-shaped or small, hard-to-reach areas, for example, dollhouse furniture or the spaces in between stair ballisters.
Sand in the direction of the grain if you are sanding wood, as sanding across the grain causes scratches. If you are not sanding wood, you may sand in the direction that is most comfortable. Press lightly as you sand, but not so lightly that the sanding is inefficient. Pressing too hard can cause damage. With a little practice you will soon find what works best for the grit you are using and the material you are sanding. Sand until you have passed over all surfaces, and you have achieved your goal for that sandpaper grit, whether it be removing old paint, deglossing or fine finishing.
Wipe the piece thoroughly with a tack cloth to remove all sanding dust. You may also use a vacuum cleaner and a soft brush attachment for this purpose. If you are sanding wood, do not wipe it with any water, cleaning fluid or oil, as these substances cause problems when it is time to paint.
Start sanding with the next finer grit sandpaper, if applicable, and work up to the finest grit, cleaning all dust off of the piece after each grit.