I've found that butchers twine works very well for cotton wick also. Depending on the diameter of your coils, you just pull away strands off of the twine. Its not as easy to feed through the coil as the Wal Mart Peaches and Cream yarn though.
You will know without doubt when the cotton is toasted, your tasters will scream at you.
As for rinsing out a head, its easiest to just toss and rewick for flavor changes. The cotton does not tend to last very long in the Kanger atty's.
NEVER attempt to dry burn with a cotton wick in the coil... It will BURN. Dry burn the naked coil.
There is an app for coil wrapping. It will guide you through what gauge wire, amount of wraps for target resistance. Check up OHMS law also.
I get my wire through eBay. Good pricing and quick shipping.
What is the app name???