Whoa, ^^^ is better than anything I can do.
My experience with building latex masks:
First, you're going to need a form. PERSONALLY, I like to make what I term near life casts. They are not as nice as real life cast, but like 10% the cost.
Yes, that is plaster wrap with a saran wrap "bald cap", vaseline any exposed hair prior to application, wouldn't hurt to do skin either.
Vaseline between the two halves as well.
Once it's dry, remove and vaseline the entire inside, tape together, then fill with plaster.
It makes a reasonable copy.
I took that, scrubbed off the vaseline with dish soap and water, then smoothed over any indents with more plaster, and shaved down the seam. Only one real flaw on the one eye. Since made many of these, most better than this first.
Anyway, for the burlap, make sure you get some decen mask making latex, and whatever you decide to do, coat the inside of that burlap so it don't itch.
Personally, I like to do ye olde cotton ball and latex buildup on the above plaster form first, then glue down the burlap to that.
Black cloth here is a barrier to prevent itching on the neck/back of head. Just a thin layer of latex.
Cotton/latex buildup.
Another, glueing on the burlap.
