Yes, you can make translucent membranes with paper mache

Interior of dragon's chest showing heart, lungs, and air sac membranes.

Last time I discussed my dragon project, I'd finished the lungs and needed some air sacs to go with them.  Bird air sacs are basically membranes, and membranes are basically translucent.  Paper isn't.  Therefore, I had to make the paper translucent.  You can do this by rubbing grease on it (remember Dr Nick from The Simpsons: "if the paper turns clear, it's your window to weight gain"), but grease was obviously out of the question.  Happily, grease isn't the only thing that turns paper clear.  Polyurethane will do it too.

What you're looking at there is a piece of toilet paper that's been coated with polyurethane.  It's not entirely clear, but it is translucent and also has a nice membranous texture.  Perfect.  Getting this effect is as simple as putting the paper on a sheet of plastic, brushing on a good thick layer of polyurethane, and letting it dry.  Once it's dry you can carefully peel it off the plastic sheet and you have your membrane.  You'll find you have the devil's own job getting it off the plastic backing, but just be patient.

Here are the two posterior air sacs prior to being inserted into the chest cavity.  They have their little corrosion cast veins in place and are all ready to be superglued inside the chest cavity.

Now, all I have to do is paint the dragon's skin and it'll be finished.