I just use the fleshy part of the finger - the nail never touches the string.
It was always a natural thing for me to use the right hand fingers to grab notes - I never really thought much about the mechanics of it until back when I was teaching a lot, and people would always ask about the technique.
Like any other technique, there are infinite ways to approach it and use it, everyone will be a little different. Some guys (Brent Mason, Scotty Anderson, etc..) use a thumbpick which frees up their index finger also, so they get 4 independent 'picking' fingers. That's one reason Brent's solos can be tricky to play for flatpick/fingers players.
Albert Lee's style is flatpick/fingers and so are non-country guys like Brett Garsed, Wayne Krantz, even Shawn Lane.
In my experience the whole key to it is having a relaxed picking hand...people often tense up and restrict themselves when first learning to do it, which can decrease endurance. You want to be able to get a good loud consistent note sound out of each finger. Especially if you're on a 3 hour gig!
One thing I would recommend is learning to use it in context of what you're already playing, instead of just learning the 'open string' licks everyone plays. That way you dont program yourself to only utilize it with certain 'pre-programmed' runs. Of course learning 'some' licks or concepts is good, but it's the type of thing that should
free up your options instead of limit you to a few little flashy 'tricks'.
Although, I will say Brent's 'tricks' are pretty fun to listen to!
