This one works for me:
Cut the polyfil in half lengthwise, or use a small polyfil.
Cut the top left (or right) 1/4 off of a PTB making a distorted "L" shape. Looking at the flattened PTB, you want it lengthwise, not wide.
Put the polyfil on the bottom of the PTB, on the side with the longer, "flag" of the L shape, and roll it up but not too tight. You may have to do this once or twice to get the right tension. Too tight, and the liquids don't absorb and the whole contraption fits too loosely in the cartridge and will pull out when you puff. It took me a couple of tries.
Fold it in half so one side has the polyfil and the other is empty PTB and insert it. Make sure you clip it off so it fits down in the cartridge; I like it down maybe 3/16th of an inch. It should not be flush with the end of the cartridge, just down a little bit.
The PTB seems to channel the liquids to keep all of the the polyfill wet, and the polyfil both makes a good resevoir and it meters out the liquid with more control than the PTB alone.
It holds twice as much liquid as either one alone.
I haven't had a single loose fiber from the polyfil - and that was my goal. That it seems to have improved the delivery of the cartridge was a bonus.
This one worked better than I hoped; if you have PTB's around, give it a try before giving up on the tea bags.
- Tinker