I suggest getting a bottle of pure Vegetable Glycerin (120ml cost me 5 bucks) specifically for lubing the two o-rings on the deck piece that the juice control glides along.
Aside from that, if you're a MTL guy, I suggest buying an authentic MTL kit, or sticking with a kayfun mini v3 (i have no experience with the mini v3, this is just what I have heard). For me personally, I use a 3mm 6 wrap 26g coil that comes out to 1.0 ohms (haven't done any fancy builds as i have no drill atm). I use a lot of cotton compared to my kayfun 4 as a solution to a slight leak i had, but that turned out to be because I did not have the coil raised high enough, which allowed juice to drip from the cotton/coil into the airflow section.
Basically, raise the coil a bit more than usual to avoid any flooding/leaking, and lube the o-rings. For me personally, I've been using this setup with the 2nd airflow setting for a nice, slightly restrictive lung hit. I would try the 3rd again, however I use heavy VG juices and I want to make sure that there is enough negative pressure to pull the juice up to the wick. That and the fact I'm a flavor junky. This was another reason I decided to use a 3mm coil instead of a 2.5; So if I didn't pull hard enough for whatever reason, there was a decent amount of cotton with juice still in it to feed the coil as I pull again, avoiding a dry hit.