I remember the carto days. Still have a few for backup. I used the condom method when I filled them. Cartos were a huge step above dripping drops into those old eGo and Joye attys. I had a short learning curve, but part of that was discovering that you couldn't drip into them and vape immediately. You had to either fill it to the top and let it soak down or use the rubber condom that came with it and fill the condom with juice, reinsert the carto, and then let it soak for a while to make sure it was saturated.