I used to shy away from this sort of work until Gigi put me straight:twisted:
So remove polish have a good look at the nails, where/if there is lifting the original appex etc.
Then don't worry about the lifting. Shorten the nails to the clients desired length, bring your side walls in nice and straight. Then de bulk the appex, now look at that lifting again, you will find that most of it has gone already and for the rest, make sure as others have said that you work behind the lifted product otherwise the tiny vibrations of the file working on the lifted product will cause more to lift. If you work behind it you will see the lifted product flake away leaving a nice flush surface to work on.
Finally, pick up your brush and use beads half the size of the ones you would for a fresh set.
Just remember to talk with your mouth not with your hands, like I do:o take your time and try to sell them a bottle of cuticle oil, retail should be a big part of our business and it helps the customer to get into some good habits:hug: