Q: Is it possible to smooth out the relief on interior textured walls?
A: You have three options. The first is to sand the texture from the wall with a pole sander. It may help to rent a dustless drywall sander that vacuums up the dust. The second method is to cover the walls with thin drywall panels, and to finish the joints just as you would with any other drywall installation. The third method is to fill in the texture with drywall compound. To do this, lightly sand the wall with 120-grit sandpaper to knock down high spots. Dust or vacuum the walls. Spot-seal any damaged areas with an oil-based primer. Thin some premixed joint compound with water using a drill and drywall auger. Mix to the consistency of cake icing. Use a 10-inch drywall knife to apply the compound in 4-foot sections using broad, overlapping strokes and feathering the edges. Allow the mud to dry overnight. Lightly sand, and then apply another thin coat. Finish-sand the wall and apply a coat of primer before painting.