Step-by-Step Instructions and Pictures: How to Prepare Wood Trim for a Smooth Paint Job

Use a non-soapy detergent (such as Dirtex, Spic & Span or TSP No-Rinse Substitute; see Buyer’s Guide) according to label directions. Regular TSP (tri-sodium phosphate) also works, but it leaves a white film that requires a lot of rinsing, and it can irritate your skin. It’s not available in some states.

Dip a scrub sponge into the cleaning solution and wring it out enough to keep it from dripping. Wash wood from the bottom upward with slow, easy up-and-down strokes so the solution has time to soften the grime (top photo). If you start at the top, the cleaner can run down the wood and create hard-to-remove streaks.

Only clean one section at a time so the wood won’t dry before you rinse off the cleaner (if directions call for rinsing). To rinse, dip the rinse sponge in clear water and wring it drip free, then wipe the surface clean in one pass. When you begin to wash a new area, start well within the clean area to avoid streaking. Change both the cleaning solution and the rinse water often—whenever the water becomes cloudy.