Ok decided to go with the green stuff.
Placed a tiny bit on the helmet and gently flattened it with a finger over the helmet. Any excess just cut off with a blade.
Next I used a bradawl with a small point to create the holes in the scrim.
Finally I cut out a thin strip and flattened it. I then cut off tiny flat strips to stick on top of the scrim.
No glue is needed and it takes about 3 mins to do a helmet. You just need to leave it dry for 24hrs.
Below is a picture of some Bren crew during painting with scrim just completed.
I guess the proof will be in the what they look like after painting and can you tell them from cast made scrim helmets ?