My juice vendor uses eye droppers in their big bottles, so the fill screw isn't an option as the dropper has juice on the outside and it makes a mess. I always take off the top cap to fill. I put my finger over the air hole before unscrewing the top cap, fill it, and screw it back on before removing my finger. I have 2 KFL's so the newly filled one gets set onto paper towel, air hole up while I vape the other. It rarely leaks by the time I get to it. Maybe a drop sometimes but nothing major.
I have to change the Ko Ghen Do cotton about every 3 tanks unless I screw up and vape it completely dry and burn the wick. Wondering when I'm going to have to change the coils? Been using the same ones over and over since using Ko Ghen Do. It never sticks to em.
This is going to change your whole world...
http://www.cloud9vaping.co.uk/epage...bjectPath=/Shops/yxve46fvrnud/Products/KAYFIL

It works VERY well, and allows for a tool-free operation.
The best thing is, it's a low priced item, made of top grade materials, sold by a top notch vendor...and not found anywhere else (via the Google search I just did)...
I have one, and it's working perfect for me.
Everyone else with a Kayfun, this is a serious piece of gear to consider having in your arsenal...
If not for filling, then at least for KF4/Nautilus style access to the coil without draining the tank!