The best way to do smile lines, is to learn how to do them with your brush.
S2 had the chance to sell these years ago ... We said no! Very fiddly sizing them up, and we would never sell a product where it was recommended that the cutter needed to be dipped into neat monomer before using it!!
I thought they were gimmicky, fiddly, and not very effective as well as a dangerous risk of overexposure to clients and technicians.
As always, the quickest and best way of doing smiles is by hand ... But of course that does require effort on the part of the technician, to practice and work hard at perfecting her skill.