Ok let me see if I can write this and it make sence
I'm going to explain about Brisa UV Gel as this is what I know about I'm not able to comment on other Gels.
If you think of it like this when you do a Brisa application you use all the correct parts of the system and this is what gives it strength and durability so if you we're to miss out a part of the system then you could be effecting the end result that your client is going to get.
As I said just applying a thin layer of Brisa and not building an Apex will effect the wear for the client and again missing out the Brisa Gloss can also effect the wear as this is what gives the final protection of the Enhancement and as Shellac is a different thing to the Brisa you will not getting the same protective layer over the Brisa with Shellac as you would do with the Brisa Gloss.
Just to say the L&P is different as once you have filed the enhancement you are finished the full application there is not another part of the system you need to apply so its fine to go straight to Shellac Colour.
I really hope this makes sence to you guys and has helped explain
:hug: