Try looking at rayon or polyester dress lining from a fabric shop. It's generally somewhat heavier than silk, but takes less dope to fill. I used it on one plane quite a few years ago. It took about 8 coats of clear before I was done, but it still had a rough surface. Sanding it with 320 and then 400 paper made it real smooth. One additional coat of clear and it was reaally glossy.
I wet covered it, pulled it tight and smooth and the dope pulled it up tight. Polyester will heat shrink some so you can be a little sloppier in application.
The film/fabric trick works too. Actually, most paints, including dope will stick well to lightly buffed film and eliminate the need for the fabric.