Sanding sealers, also called first-coat sealers by some manufacturers, are recommended when refinishing furniture. Although using a sanding sealer is a good step to take regardless of the type of stain you are using, it is especially necessary when using water-based stains. Apply the sanding sealer after you have bleached your furniture, but before you have applied the stain. Sanding sealers provide an important barrier to keep the wood pitch and stain from bleeding into the water-based topcoat. Aesthetically, using a sanding sealer also helps fill small pits and pores present in hard woods, such as oak, ash, mahogany and teak, and it helps you attain a smooth, level surface, which is especially important on tabletops, dressers and bureaus. For complete, step-by-step instructions for this DIY project, watch this friendly and straightforward video tutorial.