I occ use a efile but only for removing rockstars from acrylic or gel extensions, I remove about 90% so can see bits of the shellac or gel then continue with my hand file till all I can see is the enhancement , that's the only time I use it, I don't ever use for rebalances or other work, I do all that by hand.
It just cuts down time when removing all the shellac/gel and glitter.