swirls have been my nemesis for quite sometime too. And having crusty eczema fingers doesnt help
However lately I seem to have cracked them somewhat and with less agrivation to my fingers.
Timing is obviously very important but I also found that you dont need to hit the string over your finger as hard as possible to get the momentum going. Gently does it, and youll be suprised at the results. Hopefully a nice clean swirl!