It is essential to sand wood moulding prior to painting. The trick is sanding evenly and thoroughly despite the curves, nooks and crannies that are part of the profile of wood moulding. Traditional power sanders can damage the moulding, and regular hand sanding is inconsistent and time consuming. Several tricks of the trade will allow you to sand properly while also expediting the job.
Custom-Shaped Sanding Block
Cut a block out of a piece of extruded polystyrene insulation board, which is a compact and sturdy type of foam that's just larger than the moulding width. Don't use expanded styrofoam, as it is puffy and will not hold up. Place a piece of sandpaper face up on the moulding, shape it over the profile and tape it down. Work the foam block back and forth over the sandpaper until the profile of the moulding is carved out. Glue the sandpaper to the foam block with contact cement to create a sanding block with a profile that fits perfectly on the moulding.
A sanding sponge's cushy quality makes it another good choice for sanding contours. Apply enough pressure when sanding to push the sponge into and fill the profile. Be sure to buy a thick enough sanding sponge. If the profile is very intricate, use a thinner sanding sponge after using the thicker sanding sponge to touch up any narrow pockets that you may have missed.
Wrap your sandpaper around a pipe sleeve to create a rounded sander. Pinch the ends of the sandpaper together to create a kind of handle. Pipe sleeves are made with foam, which allows you to use pressure to easily conform the sandpaper to the contours of the moulding. Pipe sleeves come in diameter sizes as small as 5/8 inch, which allow you to easily get into narrow areas.