I have eight cats, 9 litter boxes in the house....four with pine pellets, four with scoopable litter. I use the Wal-Mart brand, Special kitty for Multiple cats. Like you, Walmart is my one of my very few options for kitty supplies. I'd love to try Tidy-Cat, but no stores here sell it.

The ninth box is essentially empty. I have two cats with litter box issues and who like to pee on hard plastic surfaces. They had developed a liking for my kitchen cupboard! So I gave them a box with nothing in it. I have to rinse it out everyday, but I much prefer that than cleaning pee of my cupboards!!!