It's possible , I've seen a hell of people doing it before ... I do it too but not so good since my spanish techniques are getting weaker cuz I don't practice much.

It's VERY VERY hard to do it without long nails .
On the other hand , you can't get your nails long or else you won't be able to tap on the elec. !

Goddamn it , I'm gonna get me some Finger Picks . ;)