OK guys I'm serious about this one. My friends and I have been doing this for years!
Take a microwave safe bowl and fill it with Simple Green. It's non toxic and the inventor actually drank it to prove it was non toxic and safe around kids. Put your bowl, down stem and/or pipe in the bowl of simple green and microwave it for 10 minutes. Poor the Simple Green into your water pipe and let it sit for 30 minutes or so. Be careful, the Simple Green will be hot! Rinse everything in hot water and then in Luke warm water. All the resin should come right out. You may need to repeat this depending on how dirty your piece is. Do this once every two weeks for better results.
This is assuming you have glass pieces. I was going to do a thread on this but I accidentally erased the picture before I could do anything with them.
haze...