Re: Mounting thin pastel papers
There's a lot of good papers available. Unfortunately Canson Mi-Tientes, while it comes in 60 colors and all of them are beautiful, isn't always lightfast. I did find some fading in old pieces I did on Canson Mi-Tientes so now I store anything I do on it in the black archival storage box from Blick. It's getting to where it's time I bought a new one since it's almost full.
Colourfix sanded paper isn't as rough as the Wallis. Wallis will eat the pastels up pretty fast compared to anything else. I think the fine-grain sanded papers like the Uart 800 grit probably don't do that as much. Also the fine grain Golden pumice ground might not be so bad for chewing through pastels.
But even on Wallis paper they seem to go a long way before being used up. The finer the grit on the sanded surfaces, the slower it goes through pastels and the more detail you can get. Wallis almost demands that I go bold with it and do big massy loose things developing detail later, like Deborah Secor teaches.
She has a good trick for toning white Wallis though. Scribble over it loosely with the side of a stick and then scrub the powder right down into the tooth with a big wide foam brush -- the hobby kind of foam brush. That will tone any white sanded pastel surface to a lighter version of the color you used for toning and not use up too much of it before you start adding other colors with heavier strokes.