In the end...no matter how good or shitty a job you do...it'll be up the the host and/or field owner to determine if you can use it.
A couple of points:
1. DO NOT use ski goggles...they look the same, sort of...but they may very well be unable to stop a BB. At the very least use ballistic mil-spec goggles...or Paintball Goggles.
2. From the jist of what others have posted...stamped (i.e. the holes are punched out of a solid sheet of metal) mesh holds up much better than woven (i.e. wires are woven into a mesh) materials.
3. Doubling up makes it more deformation resistant/durable but cuts down on air flow.
Lots of guys have done this already (well...at least the mask part). One of the local guys here has a little one he keeps on with elastic straps....kind of like a small surgical mask, but out of mesh. It works...but it sort of looks like a mini jock cup
There's a couple of threads already on here where guys have posted theirs.