the nano is not easy to work with at all, the filling valve sux, well if its a clone, not sure about the real thing
whati do is i make a macro coil with 28ga kanthal like around 5 or 7 wraps, just a little cotton that u cut right at the top of the inner chamber tube, then u push the cotton back in.
put a few drops of liquid in there, then fill it from above while closing the airhole with ur finger.
just close the top cap for like 1 turn, maybe half of a turn or something. put the whole thing upside down, wait for a bubble to come on top (so near the base, then close it completely, and u done
not that easy, the real kayfun, i mean the bigger one, the 3.1 is way easier and to me the vape is better than in the mini clone, but that mini is doing a good job