personally, i don't use any substrate at all.

when there's a big poo, i pick up the "solids" with a cloth, shake the "solids" into the toilet, and put the dirty towels in what i like to call the "snake waste genie" which is essentially a container with a lid so i don't have to wash them immediately (cause it would be silly to do a load of laundry for 1 cloth).

then i wipe up the wet stuff with another cloth, rinse that, and also into the snake waste bin it goes. then i spray out the tub with 1 part vinegar 2 parts water to clean it and deodorize. about once a month they all get a total washdown in the shower.

works for me, is environmentally friendly, and doesn't waste money on paper towel.

yes, newspaper is pretty much free, and recyclable, but i don't think you're supposed to recycle it once there's poo all over it haha.