99% of my clients are overlays. I hardly ever do extensions and if I do, it is usually for a new client until they grow out their own nails.
The times when I do sculpt, I use CND performance nail forms which are much easier to use than the other ones I have tried. You can buy them from S2 :
0845 210 6060
Calgel is one of the easiest product that I have used, but if you are used to using L+P then gel may be a little tricky for you to start of with.
If you are creating an overlay, then use the gel almost like a nail varnish and brush it on. With overlays, you don't need much of an apex so create layers until it reaches your desired thickness.
If you are doing a sculpture, then you need to change to a different technique to create the enhancement. Do not 'brush' the gel on, instead, try to 'dangle' the gel on to the nail making sure you have created the bulk of the thickness where the apex is for stronger nails.
I always make my nails very thin at the cuticles whether it is an overlay or extension. To do this, I use the 'push and pull' method making sure my brush has the correct amount of gel and not overloaded as this can flood the cuticles. The push and pull method can be learnt here on one of Gigi's articles:
http://www.salongeek.com/nail-finishing-maintenance/11972-precision-polishing.html
Hope this helps.