I collect Busch light 12 pack cartons cause I drink a lot of Busch light.

I use them for all kinds of paint related situations.

This might be one of them where I would lay out maybe 8 of them and pour the paint on them and let them dry.

A piece of Visqueen would work too.

I admire your resolve in helping to maintain the planet in some sort of working order.

Kitty litter really doesn't work on full gallons, or even gallons that are more than half full. Even a quarter gallon is pushing it.

Just let it sit ,( a couple weeks, preferably out in the sun) it WILL harden if there is litter in it.

For future reference and just general knowledge, habit for humanity will take paint.

I was just going to recommend donating it.
I pick up some great paint at reuse centers. Primers, faux finishing products, etc. It's a shame to let that go to waste!

Is this paint latex or alkyd?

I had some half full 5 gallon buckets of latex and a dozen nearly full gallons left in the barn by a former owner, frozen and ruined. I just checked and after 18 months they are finally dry enough that the trash will take them.

If you call a paint store they usually can tell you where to recycle paint (some paint stores act as a recycling center) or call your city- county recycling facility and they can help you. Community theaters or high school theater groups usually are happy to accept paint for use in painting their sets. Your paint can't be used anymore, but for future reference...