i usually use the crushed shell on the smile line to enhance it. curve it round and keep it thin.
I apply shelly's between the layers.
With a Refill>
I take off the old Design and blend it,then I apply a thin coat,then go in the Lamp, then I apply the shell's - one more time in the Lamp. Then I build the Arch with the UV gel over the Shelly's and after this coat is hart i file it in shape. Top Coat and done
Shells and other Nail Art stuff that would make the Nail to thick I always apply it between the the 1st thin coat and the coat to built the apex. ( Sorry I don't know the professional terms for it)