Application of mink lash extensions

Hi there, I've been dong lash extensions for around 3 months now and normally use b curls from lash base, i was wondering about trying the 0.07 mink lashes from Ah Francis, but I believe you layer these up, putting up to 4 on each actual lash? Does anyone else do these lashes and if so would you just grab say 3or4 lashes and put them on at once, or would you do a full set then go back over and re-apply? Hope someone can shed some light, also would you charge more for these as the lashes cost more and I'm assuming it would take longer?.