My husband and I are finishing our basement in a 65 year old house. We have a cinderblock wall that is next to our staircase. Our staircase is narrow, so I thought utilizing the german schmear technique would be a cool way to cover up the cinder block without taking up too much space. My vision is to do a heavier mortar so it looks more texturized like a plaster wall but I am having trouble finding anything online about using this technique over cinder block and looking for recommendations/if this will even work. The cinder block is painted already with a waterproofing paint, however it does still have some texture to it that I think the mortar would stick to.