I've only been making my plaster-gauze masks for just a few months, and am not as experienced as Jonette, but I will tell you how I do mine.
I usually do two layers of plaster gauze on each face and don't wait for it to dry between layers. I sometimes do one layer, but that makes for a very delicate mask and will break easily if not careful in handling it (the one layers are my favorites and turn out so much prettier). After my model takes the mask off, I mix a small amount of plaster of Paris (the good stuff), or precious stone and "paint" over the entire mask with a brush or my fingers. I then lightly sand any rough spots and fill in where needed. I do all the sanding, filling in, etc. while the mask is still wet. It's easier for me to do it this way. I know they are dry when I look at them under a bright light, or in the sunlight, and don't see any "dark" patches or "water" spots. I let it dry for five or six days, just to be sure they are dry. They feel heavy when wet, but get lighter as they dry.
The masks are very light weight (around the weight of Jonette's, lighter if I use just one layer of plaster gauze. The more layers of plaster gauze you use, the heavier the mask is. Although messy at first, I've learnt how to make them with minimum mess.
I paint them with acrylic paint most times, but have used regular craft paint as well. After they are painted, I spray a polyurethene, or clear fish matte coat on them, then add the embelishments.
It's really not as hard as some may think. I used straws for the nose openings when I first started, but have learnt how to do the nose without them, and my model has no problems breathing. I'm working on incorporating the ears also. This is a little tricky, but it can be done, and earplugs with a little cotton over the ear opening keeps the ear dry and safe as well as keeping plaster from going inside the ear.
Some of my masks are now in the gallery, if you'd like to see them. The Jester (my daughter's employer's face) and Little Warrior (my 3 yr. old granddaughter's face) are my most recent ones. The others are some of the very first ones I did while learning to make the masks.
Adrenna