it the enclosures that i have messy poopers in i run a thin bead of clear silicone between the cracks, keeps anything from falling between makes it easy to clean, if you keep it thin its not even noticeable so its not gonna look tacky or anything, and it comes right off with a razor blade if need be. comes off pretty easy, i just tore down a few cages to get ready for the move and it peeled right off.
i dont use sand so im no help with that. for the couple sand boxes and lay bins i have i always just throw it out, its only 3 bucks for a 50lb bag anyway.