Just to muddy the conversation up a little more, I don’t make contact with my nail to the yoyo during a fingerspin. Fingernail fingerspins seem more popular, but I’ve even read some people say they prefer fingertip fingerspins with little or no nail. I have to do them this way since I don’t have long enough nails. You can do them using only your fingertip and get really pretty good results with some practice, even if the skin contact makes the yoyo die quicker than nail contact would.
One thing I consider key with fingerspins is keeping your finger loose. A stiffened finger makes the yoyo shoot right off my finger after only a spin or two. I let my finger move with and be controlled by the yoyo in small movements and that seems to help.