Have you tried just hot water? For daily maintenance I often find a good flushing with hot water from the tap is good enough to clean most residue. After about 2 weeks I break down and clean with rubbing alcohol as Tiny said. 70% will work just fine and runs about 2 bucks a liter I think. Just splash it around with medium coarse rock salt or rice and your clean as the day you bought it. The salt or rice act as scrubbing agent and works fantastically but they will wash down the drain no problem.