I have used paper towels, but I've found that the blue 'shop towels' fit very nice and neat into my tubs. They're also very sturdy and provide a bit more cushion than paper towels.
i use calcium sand for my adults and paper shop towels for juvies and babies. however everyone has me freaked out about the calcium sand so i think i will change it to play sand here in a month. i have heard horror stories about calcium sand but never had a bad experience in 2 years with 4 leos. they always eat the crickets off the sand and worms off a dish. maybe i am lucky?