One of my cats consistently pees over the back of the litter box. I finally bought a tote container to keep the wall clean. I laid the tote on on its side and slid the litter box inside. It hasn't helped with the cement on the bottom of the box, but I can rinse the tote easir than the wall. Even the cats that don't like covered litter boxes will use the ones with totes.

I tried the Pam spray and found that it really helps. Gotta be careful not to use too much; it's kinda messy if you get it on anything else.

Wish I had a cure for the cement problem but I can certainly can commiserate.