A point will be reached at which your pipe is caked solid. Time for a big cleanup. Crack is highly soluble in alcohol (ethanol). You run a cubic inch of ethanol through the pipe, reusing it each time so as not to end up with too much solution. It doesn't matter which grade of ethanol, the higher the better of course, but in a spot you can use vodka (although you will then end up with some sugar in your resin). Caution: wait till your pipe and chore are no longer hot before pouring down ethanol, otherwise your pipe will go off like a musket.
Once the resin is cleaned from the pipie, squirt or pour the now honey-couloured ethanol onto a soup plate and leave to evaporate. The crack may condense in cute golden flakes on the plate rim. Before pouring the ethanol solution onto the plate you may want to filter it through a common coffe filter: this will remove any soot.
Some people advocate setting fire to the ethanol. You should only do that if you're sure you're ethanol is not high grade, ie if you're certain it contains a good deal of water. The logic is that the ethanol burns and vaporises some of the water with it because of the temperature. Within 20 seconds you're left with just a tiny weeny bit of water to evaporate. This is a shortcut compared to waiting out the low-temperature evaporation. I tried it once and before I knew what hit me I had flames up to the ceiling. No harm done but I swore to myself never again to put a flame to ethanol. Better bide on'es time.