Just buy a glass screen, not those metal ones, but you can buy small, glass screens that are usually in a star shape, or in form of a glass jax piece. A little stem piece fits right in the bowl hole, and keeps the ash from going in your mouth.

Like, $2 a piece at any headshop. Give it a try. It's what I use in my bong, steamroller, and bubbler, and glass spoon, no ash in mouth.