I found a thread or you tube video where you take a regular 510 cart, and pull out the filler. Cut it exactly in half. Fill up the cartridge to within 3mm or so. Then carefully put the filler back in. Make sure that when you cut the filler, to keep the fibers running in a similar direction. (you want the fiber ends to be at the tip of the cart) Put the filler back in carefully. its ok to press the end that is first going into the cart into a slight triangle so it fits in, but you want the face to be fluffed out, so that it compresses back together when stuffed into the cart, so that leakage does not occur. When you press the cart onto the atty, the mesh pushes the fill just slightly into the right position.
you will need to top off once you put the filler in there, until the top looks just like a slurpee (cant remember who said this, but it is a perfect description)
I was a big fan of the Tea Bag mod but not as much now. I can get more juice in with this technique. For some reason I was getting some leakage with the tea bag mod, and sometimes dry atty.
I find if I am careful, and not run it dry, you can reuse it nicely 2 or 3 refills. I receive a piece of fluvall filter (this stuff I got is white and fluffy and looks just like what came in the cart to begin with, but the person that sent it to me says its a lot better, and it is less prone to burning.
By cutting half the batting out of the cart, you are leaving more room for juice when you fill it. Just be careful for leakage, and I probably would not use this technique with an automatic battery, as the leakage can fry the battery. I use and Ego, and it has not leaked. I will try these carts it this weekend with my wifes auto vapor king 510. (I have auto and manual batts)