Drain your pool down to the area of the plaster that you want to repair and polish.
Scrub the plaster surface using an algae brush, which has stiff bristles to handle stains and debris.
Polish the surface with a pumice stone to remove stubborn stains.
Apply a pool patch material to any areas that require repair with a pool trowel. The mixture is made of cement, sand and acrylic bonding agent and should be mixed according to the manufacturer's instructions.
Smooth the edges of the pool patch mixture using the trowel. Wait for it to dry and harden.
Rub the edges of the hardened pool patch material with the pumice stone to wear it away and blend it with the rest of the plaster surface. Add a little water to make this easier.
Polish the entire surface that you patched with the pumice stone to even it out and make it nice and smooth.