I have used wet strips of papertowels instead of Vaseline. Tear strips and
pieces to fit the face, dampen them and place them on face. The gauze strips
work well on the paper towels. The drawback is that not a great detail can
be achieved with the paper towels being in between the gauze and skin...BUT,
I believe this is a much safer way to do this project. Make sure the
students' hair is tied back or the plaster will stick to it. If you do
decide to use Vaseline put plenty of it on their eyebrows or they will lose
them! Some students may be allergic to the Vaseline and have a "red" face
after the project. Also, middleschoolers have enough acne w/o adding more
gunk to clog their pores. These are some of the things I think about!
Good luck and let me know if you need anymore help.