Not sure how or why it works, but we stumbled on a nifty small homemade hitter that repels resin buildup like magic. A bottle from Star white wine vinegar, a Dremel tool and about a half hour or less. The little bong you can make from it hits really well w/zero splash due to the bottle's shape. Unreal, but the thing just doesn't take on a resin buildup at all. Always looks like I just gave it an alcohol/salt bath.