To do this I simply used my everyday nail polish remover, Sally Hansen Strengthening Polish Remover, which I poured into a shallow dish - I couldn't find a shallow dish so I actually used the lid of some Johnson's Cotton Buds! I know it is possible to buy pure acetone which will obviously be more effective, but I don't know where you buy it from so I stuck with your bob-standard nail polish remover.
Then, I simply dipped my hands into the dish and waited. Usually it is recommended you wait 10 minutes but this is with pure acetone, so I waited more 15 or so minutes. Then I used a manicure stick to scrape off the Shellac polish. Most of it came off pretty easily, I did however have to dip some nails back into the dish because there were a few stubborn bits left behind.