I built my nano with the supplied Clapton coil and wicked it with dm Viskose (dm Rayon balls). I prep the dm ball by unrolling it and folding half back on itself. Trim off the fold and form a round wick on that end. Pull enough of the wick through, holding the coil in place with fingers or a thumb nail. I cut off the long excess and pull the wick back and forth in the coil. Fluff the ends out with a pin, cut the upper 50% of the tail 1mm from the coil end. Trim the remaining tail even with the edge of the base, fold and tuck into the juice holes. I usually poke a pin down through the wick tails quite a few times where they enter the juice holes, just to make sure they are fluffy and not bunched up. Prime, fill and vape!
My wick tails poke a little past the holes, I vape MaxVG juice on the provided Clapton at 60W without any problem. You can always pick out a little bit of the wick going into the holes later on if it is too much.
Rayon is NOT used the same as cotton, much more density in the coil and the tails thinned out by 50% or more. With the proper amount of Rayon in a 3mm coil on the nano, you could probably thin the tails by 70% and not have any flooding after you fluff the tails and tuck them into the juice holes.
@ricks uses 100% PG I think, so that would require much less thinning of the tails.