How to Paint, and Cut Trim on Walls

Measure the amount of trim needed. Using a tape measure, measure each segment of trim needed for your wall. If you're only installing baseboards, measure wall-to-wall, including segments divided by doors. On a sheet of paper, mark the length of each segment separately.

Purchase trim. Add each measurement together so you know how much trim to buy. Choose unpainted trim. Trim often comes in 8- or 12-foot pieces. Make sure you have enough pieces that you won't need to add together several pieces to cover one wall segment.

Cut the trim. Take each piece of trim and, using a tape measure, mark each with the length of a corresponding wall segment. Cut the trim using a coping saw. Cut whole segments as much as possible, piecing no more than two to three segments together for extremely long walls. Set excess pieces aside.

Sand each piece of trim using 120-grit sandpaper. Make sure to smooth out the newly cut edges.

Wipe the trim clean with a wet washcloth. Rinse out your cloth intermittently to ensure that you remove all particles from the trim. Let the trim air dry.

Prime the trim. Using a small paintbrush, apply a thin layer of latex primer to each piece of trim. Allow it to dry for several hours.

Apply one coat of latex paint to each segment of trim once the primer has dried. Allow the trim to dry at least one hour, then apply another coat. Paint up to three coats on each piece of trim, and allow it to dry overnight. Your trim is now ready to install.