Quick and dirty cotton application on hurdy gurdy

Rub the string lightly with the rosin block, make sure not to damage the string.
Add a small and very thin bit of cotton, make sure it is very even and without knots.
Lift the string with your finger, turn the crank slowly and bounce the string onto the wheel a few times to feed the cotton under the string. The cotton should be wrapping itself around the string with some help of the other finger.
Make sure the cotton sits very even on the string, you can spread it a bit using your fingernails.
The cotton will unwind when you crank backwards, so be careful not to do this.
Check cotton condition regularly, also check under the string.
Remove all cotton before adding new cotton.
Too much or uneven cotton will cause tuning issues and noises.