I use shredded aspen or newspaper. Newspaper is free but not the best for soaking up anything wet.
I feed in my cages even with aspen and never had a problem but it does sometimes worry me.
I use cypress mulch on the big cages, feed in the cage no problems...

I will say that years ago I used cypress mulch and had a ball python get a sharp piece that pierced the inside top of his mouth(he was fine).He wasnt even being fed so I think it was just a weird thing that has never happened since.

The quality of cypress has gone way down.The stuff at walmart is so full of large splinters its almost not useable anymore.Ive been looking for alternatives for the large cages.