**Bare drywall: yes, prime before painting.** Once the joints and patches are finished, completely dry, and sanded, remove the dust and apply a drywall primer. It equalizes absorption between the drywall paper and joint compound, helping prevent patchy color and sheen. [Gypsum Association guidance](https://www.gypsum.org/wp-content/uploads/2011/11/232-04.pdf)

**Existing painted, textured walls: priming before mudding depends on the surface.** Sound, clean paint can usually accept joint compound after scuffing and thorough dust removal; USG recommends that preparation for previously painted wallboard. Remove loose paint or texture and clean off grease first. [USG customer-service guidance](https://www.lowes.com/questions/sheetrock-brand-381630120-drywall-joint-compound/3009547/86561c6e-4740-5328-8bcc-37a2e6e461f0)

For glossy paint that you cannot thoroughly dull—particularly in the texture’s recesses—use a bonding primer approved for the surface and for application beneath joint compound. Stains need an appropriate stain-blocking primer. Follow your compound’s preparation instructions.

**After you skim coat, prime again before painting:** let the mud dry completely, sand it, remove the dust, then prime the entire skimmed surface. [USG finishing guidance](https://www.usg.com/content/dam/USG/pdpmovedocuments/usg-sheetrock-ap-drying-type-powder-joint-compound-submittal-52925.pdf)