I am trying to paint a blanket in a backpack of a WWI soldier. I want it to have a rubberized side face out. Not sure how to approach the rubberized side of the groundcloth. any help is appreciated

jay

Painting it in oil paints will give a satin finish. Alternatively some diluted satin varnish applied will work.
Also worth looking at using diluted ink over the piece which will give a satin look if you build it up.
Sometimes mixing flat paint with gloss can give you the satin look but this is probably the most difficult to control.

Try the techniques before you do the real thing.
Gells