First up is the condom method, not sure how well it works on the Xl cartos, but on regular sized ones it's easy as pie.
A Great Way To Fill Cartomizers - YouTube
(I even loaded it up to where he gets on with the tutorial)
The other way I do it is by tilting the carto around 45deg, and add drop by drop. Wait for it to saturate, rotate carto, couple more drops. Keep doing this, slowly adding drops to the filler (don't get any down centre post if you can help it). Let it sit a little bit, if the filler on top looks like a slushy it's about full. Wipe the outside, on mouth end blow through carto into a paper towel to get any juice out of the centre hole. It's recommended to let the cartomizers sit for ~10-15 minutes to become fully saturated at the coil, burnt filler tastes horrid and once it's burnt it'll keep that flavour.
The Smoktek looks like it holds ~3ml, that'll be 50-60 drops.
As to the Kanger I think they're standard size and should hold ~20-25.
Always blow down into a towel and wipe the battery connection after, this will help prevent flooding/overfilling. After you fill a few times it becomes SOP and you won't really think twice about you're doing.
Happy vapes!