I'm glad you asked, becuse it gives me the opportunity to tell you how Creative teach rebalancing! Firstly start by using a good sharp new abrasive always for the rebalance - makes the job much faster and easier.
MOST technicians when faced with a rebalance or 'fill' as some call it look at the nails and go straight for the problem area on each one - i.e. the lift if there is any. And yes, if that is what you do then filing thru the product immediately would be time consuming as you say. BUT if you tackle the job Zone by Zone - in the same way as you would apply the product
starting at Zone 1 (the tip) first and thinning and shortening it -
then zone2 (the stress area) thinning it and checking for any cracks or weak spots, -
then when you get to zone 3 (the cuticle area which is already the thinnest zone anyway, and where the lift will be if there is any) you will already have been thinning it during the process of preparing zones 1 & 2, so the job will be much easier when you start to work on that area.
One thing you must look at is whether or not you are getting more lift on your product than you should be. Newbies always get lifting at the sides and the cutical area because they go too near or touch the skin with the product in the first place. Sometimes the lift is due to product being applied to thickly (another part of your learning curve). Keep a small space free of product when you apply and lift will become a thing of the past or at least a rarity. there are some good threads on lifting on the board - have a look at them too.