I use a knife.. then I move to a paper clip for the smaller areas. Then I just run it under hot water... sometimes I put some salt in the pipe to get some friction going.. that seems to work really well at getting all the resin out. I've boiled my glass pipe a couple times, but I've heard that this can lead to cracks in the glass, so I stopped doing it. Is that completely wrong, or will boiling damage a pipe?