NSD Bett Vernon became a NSD doing it this way (and she taught me!) -
At the start of the SCC I say,
"Tonight we are going to be concentrating on skin care and not glamour for 3 reasons:  1) not everyone wears glamour cosmetics; 2) color is a very individual choice and 3) to do everyone individually tonight would take too long.  So, if you are interested in having a private color appointment with me so I can help you choose your most flattering colors, sign your name on any time slot that is open in my datebook.  If you choose a time that is highlighted in pink, your lipstick choice is on me!"
I also add to write down besides their name if they want to learn about eyes, lips, cheeks or a little of everything.
I then pass my datebook around the table and they sign up.  I highlight the times I would rather work in pink, that , lets me control my time rather than the other way around.
PJ
P. J. Kitzler
Independent Beauty Consultant