Dump all the crap out. Rinse in hot water, repeat. When it's all out and you've just got that crap tar residue left, use a mixture of rubbing alcohol and salt (as mentioned). Its for the abrasiveness and doesn't dissolve in the alcohol easily. The tar will then wash right off. Also, you could use something called Formula 420. It's essentially the same thing, but works and smells better. But, of course, you gotta pay for it. A three pack of 12oz bottles is $15 online.