Usually its just gunked up cotton not so much the coil. Before I got into rebuilding I just ran them under the tap a min or so. put your finger over the end and blow out as much as you can through other end. Wrap in paper towel, few more blows then store them away and use next coil. You can do that to each 3 or 4 times before it's nasty. If you don't want to rebuild the BF RBA they are still a good option because you can just remove cotton, dry burn coil, run it under water, dry burn again and they look brand new for couple months easy. Just replace the cotton.