First thing is I do this upside down. Not me but put the tank into the thingy upside down so the carto threads are in the cap end then after putting the cap on flip it so the cap is facing down. The reason I do this is because if you fiddle a little much it is easier to wipe out the shallow cap than the bottom of that deep slender bottle.
An XL cartomizer takes a little over a ml to fill but once you do have a ml in it thats enough to get it going. So going by that it would take about a third of a tank on a 19XL. No rocket science on this, as long as you have enough liquid in there to have the coils wet you will be fine. if you put in too much it will over flow down the middle of the carto and a short puff and wipe up will fix that.
I usually take the tank out of the thingy several times as I think I am getting close to full to look at the filler. If it is beginning to get that wet look on the filler material then it is done or maybe just another fiddle or two away. Also look in the cap (if you are fiddling upside down) for a drop of
eliquid, if there is a drop in there you are likely done. just how many times depends on how well it is working, this is dependent on how thick the liquid is and how energetic you are about your fiddlin.
Dont forget to start it out slow, those first few pulls on a cartomizer can make or break it. Low power if possible and very short one second or less taps on the power button during a full regular draw. Do this several times even mixing in draws with no power button at all until you get the hints of flavor and vapor. Then begin to gradually add more power into the mix. This part is crucial as it helps to ensure the liquid is fully to the coil before applying enough power to make the coil glow. Once the liquid is there it will prevent the coil from being able to glow as the energy is being transferred to the liquid to vaporize it.
