Also as gibran likes to point out, DMT seems to like to stick to itself so the more DMT condensate and residue you have in your pipe, the more vapor will get stuck to that condensate and just end up creating more and more condensate instead of making its way into your lungs. This can create a non-linear situation where you begin to have more and more DMT condensate buildup and less and less being able to make its way to your lungs. When you wanna clean it, you can use 92% isopropyl alcohol to rinse out the pipe, and then collect the alcohol used to rinse in a bowl/tray and allow it to evaporate in a well ventilated area over several days. When it's pretty much completely dried but still a little moist is the best time to scrape it out of the tray and then allow it to air dry a bit longer till it no longer smells like alcohol. I wouldn't discard anything dark or brown that you get either. I've found the dark stuff to be highly psychoactive and while colors normally don't matter, I've found practically beyond a shadow of a doubt that if I get dark stuff in my GVG from overheating, that if I clean it out (which is usually hard to do since it is a bit resistant to the alcohol - but nothing that a good consistent shaking won't fix) the dark stuff is significantly stronger by weight than pure DMT and has helped me facilitate some of my strongest experiences with shockingly low doses.
You could try warming the alcohol up in a heat bath as well. pPut the alcohol in a shot glass / similar, boil the kettle, put a little water in the bowl, place the shot glass in the water for 5 minutes and then use to clean the pipe. I would cover both the holes and give it a good shake n swirl... IPA works great IME