Steps:1. One possible solution for repairing the risers would be to apply stripper and remove the old paint and glue residue, but this could ruin the finish on the adjacent treads. But it's easy to apply a new layer of Masonite over the risers, providing a smooth, clean surface to paint.
2. Measure each riser and be sure to check each step as the risers may vary slightly.
3. Using the table saw and power miter saw, cut the 1/8-inch Masonite to the measurements you took earlier (figure A).
4. Paint the treads before installation (figure B). This will save a ton of time. Make sure to paint the back, front and edges of the Masonite. This will prevent the boards from warping as the paint dries. (Note: Paint causes moisture content of wood to rise as you paint and fall as it dries. If the front of a board dries more than the back, it will warp. Thats why it's wise to paint both sides.)
5. Simply slide the new riser panel into place and attach it with a few brads using the nail gun (figure C). Dont glue the panels in place, in case you ever want to remove the panels later. Glue would ruin the risers even further.
6. Fill the brad holes, touch up the paint and it's finished.