Prime bare drywall before painting. Once the joints are finished, dry, and sanded, remove the dust and apply a drywall primer, commonly PVA. The primer evens out absorption between the drywall paper and joint compound, helping prevent patchy color and sheen. [Sherwin-Williams primer guidance](https://www.sherwin-williams.com/homeowners/how-to/painting/interior-painting-how-tos/sw-article-dir-intchooseprimer).

Existing painted, textured walls don’t always need primer before mudding. Joint compound can generally bond to paint that is firmly attached, clean, and dull. Remove loose paint or texture, clean off grease and dirt, and let the wall dry. Lightly sand glossy paint to dull the sheen. [USG surface-preparation guidance](https://www.usg.com/content/dam/USG_Marketing_Communications/united_states/product_promotional_materials/finished_assets/sheetrock-wall-ceiling-texture-application-tips-en-J1828.pdf).

For adhesion problems, stains, or exposed torn drywall paper, use an appropriate bonding primer, stain blocker, or problem-surface sealer before mudding. Follow the product’s instructions for compatibility with joint compound. Ordinary PVA drywall primer is meant for a different purpose.

After skim-coating, prime the wall again before painting. Let the compound dry completely, sand it, and remove the dust. Then prime the entire skim-coated surface for an even finish. [USG finishing instructions](https://www.usg.com/content/dam/USG_Marketing_Communications/united_states/product_promotional_materials/finished_assets/sheetrock-lightweight-settingtype-joint-compounds-easy-sand-submittal-J621.pdf).