In my opinion anyways. I've never had problems using these methods. I always use color changing glass bowls and glass bongs, Never metal or acrylic or wood.
Most effective if you plan on smoking the resin in times of emergency etc.
Paper Clip: Take a paper clip(one of the big ones) be careful as you scrape the wet resin out of the carb as I have seen someone break their carb with a metal coat hanger. Put the balls of resin on a rolling paper focused in one spot or you can roll it between your fingers to form a big ball, I have gotten a golf ball sized resin ball from one pipe!. When you get all you can, I have managed to be able to clean every part of my pipe with a paperclip through the carb and mouth piece, tear off paper as needed or cut pieces off and then smoke it tastes bad but it does get you very high! I only do this in times of need. Usually I keep a roach collection for rainy days, I think I'm up to about 40 or 50 now.
Take a pot and a pair of tongs. Fill the pot with water and get it boiling on the stove. Take your pipe and carefully set it in the boiling water(you can put your pipe in the water and let it heat up with it). Carefully shake it around in the boiling water with the tongs and you will see the brown resin start to come out. It only takes maybe 5 minutes to do this, anything that gets stuck use a paper clip to pry out, it will be loose and should fall right out. After this your pipe will look like when you bought it If you want to smoke the resin simply take a clean plain white t-shirt and stretch it a little bit then shake the pot a little to get the resin floating around and strain it through the t-shirt. Set it down and let it dry out a little but not too much, take a clean razor blade and scrape the shirt where the resin is to get it into one pile. Let it dry out full now and you have resin whether its for a rainy day or you like to put it in your joints, etc.
These are the methods I've used but I have heard rubbing alcohol does the trick, it doesn't hurt your piece but it could fade the color. Happy cleaning