Apr 29, 2019· Spray the cinder block wall with a hose to rinse off most of the debris. Look for tough stains, damaged spots, and other issues you need to address. Spend time lifting stains with soap, trisodium phosphate, and other cleaners. Also, clear debris out of damaged spots and repair them. To repair damage, mix mortar. Fill in the gaps to level out the wall as much as possible.