@meeper ok toilet paper or a towel can works- but if you haven't tried sponges then do try because:

- it's softer than most things
- has air in and holds water at the same time, so when pressed water comes out at the same time cleans (acting like a small wash with wipe that doesn't create sores too easily which fixed material can encourage)
- can be found free in recycling bins (usually plastics are clean) / cheap new / left over insulation type stuff you might have already.

I had left over sponge/insulation stuff (like what you get in cushions, crappy stuff, not fiber glass etc) but as a rectangle mattress piece / block which I cut off almost never and will last me a last a long time.

I also cut off and use to wash other things so it's multi-pupose material like using a mini spongebob !

It's a lots softer / cleaner / reusable even compared to paper or towels and ideal when it comes to minimising bum sores like haemorrhoids soaking the sponge a bit and washing right after. Small ice-cream tube might help keep it somewhere.