Tazz,
Sorry I'm not being clear.
If I have a litter box that does NOT have the grid I will use the Care Fresh. But it IS expensive.
So I figure I can use regular (and much less expensive) kitty litter with the shifting litter box because the bunnies cannot get at and eat the litter. And actually I go even a little farther with all my litter boxes regardless of what type of litter or box I am filling...

First I put down a thin layer of baking soda, I sprinkle down about 1 cup over the entire bottom...it helps control odor. Then I'll put down about 2 inches of the granular litter and put the shifting tray on top. Then at one end...I'll put down a handful of tim hay and I leave it bunched up so that it is not covering up the entire grid, just a few inches of it. My buns got the hang of it right off, plus like I said they relax and even snooze in the tray when they're done snacking.
Also, did you know that white vinegar is a GREAT disinfectant and odor killer for litter boxes and floors (if there's an accident)?
I hope this helps you.