I like the condom method the best with any carto...For some reason it seems to really soak the carto the best...I dont even remove the rings for the first fill...Honestly I havent even been using the Drip tips for a couple days....I have also been using the KR808 Jumbos though that dont get as hot on the lips because of the length and they hold a full 2 ml of liquid so the filling isnt as often.
When dripping into the cartos I like to take the drip tip off if Im using one. Makes it easier to get the liquid around the sides of the unit.
I wasnt going to say anything, but Im using a 3ml 2.0 Ohm carto right now that I had made....Great vapor and flavor...Down side is that is slightly too wide, so the Darwin dosent close all the way with it on, so it will probably be 30 days or so before I get them in the right size

I really think you are gonna love the 2.0 510 though...I never liked them as much as I do with the Darwin.
Drew