Hi, I use NSI balance hard gel so can't comment on Brisa hard gel I'm afraid. However, what I usually do for a repair under shellac is apply a very thin layer of clear hard gel then embed the silk over the split and push down firmly with my gel brush, then I cure, then I apply another thin layer of hard gel over the top and cure again. I then wipe the inhibition layer off with d-sperse and gently buff with a white block to ensure a totally smooth finish. I then proceed with shellac application as normal. The repair is then just left to grow out.
If you repair with the BL sculpting gel (remember you do NOT need silk) then if you choose to soak off the whole enhancement, as opposed to rebalancing, then obviously the split will be visible again until you reapply the BL sculpting gel again.
I was advised that the smoothing gel is not strong enough for repairs and you need the BL sculpting gel for that job instead.
Hope that makes sense x