Our previous kitty LiL Sadie peed a lot, clumping was awful as I would end up with just large blocks of wasted litter. Feline pine solved that.
I would use a flat non sifting shovel, move the upper layer pellets aside, scoop the sludgy dusty stuff off the bottom, and then
fill back in with pellets. It wasn't perfect but a bag of litter certainly lasted a lot lot longer with her. And smelled better.