I feed in a different box. My snakes have no problem with this. I just put down some paper towels in a rubbermaid, put my snake down, do the "mouse dance", wait for digestion, carefully put my snake back, and then presto! easy clean up.

Also, by feeding outside of the cage and on paper towels, my snake will never ingest substrate while eating food.

A piece of plexiglass cut to match innder top of the tank can also help to keep the humidity (only cover 3/4 at the most though, so your bp still has airflow).