It's nearly impossible to clean the interior, but soaking in solvent or parts cleaner, with a good rinse and compressed air dry, wouldn't hurt. This assumes they are removed from the head. I cleaned the exterior with a wire brush on the end of a drill. When clean, they drop right into the head, no hammering (in OR out) required.

I almost forgot about the possible prechamber seating issue, when using vertical prechambers on a newer (17-22 casting) head. Ugh! Let's just ignore that until the problem actually appears...