Lay the facts out straight and simple, let them make their own choice and if they can't do it, leave them. They will know what to do if they change their minds and want to follow/join in. If there is a strong woman in the group point the others to her. Also...

A: everyone is in the same situation so we all look alike.
B: we can clean up and primp after its over.
C: both A and B apply to the male dandies out there.:)
D: no matter how well you explain it or how much help you can give some people just can't do it, even with time for reality to sink in.

Just my thoughts but I'm not the kind of woman who spends a lot of time dressing like I belong in a display case.