You can feed in a tub with substrate. Mine get mouthfuls of pine shavings fairly regularly and everyone is healthy. They evolved to eat on jungle floors which are loaded with undigestible garbage, a little bit of wood shavings or coco husk won't hurt them.
Depends on the substrate. Reptibark definitely can be an issue. I've used it with hatchlings in the past and on multiple occasions had a piece become lodged between a python's jaws vertically upright. Not a fun scenario.