wslade2, I restored my glareshield earlier this year. Mine was structurally in decent shape, so I had minimal work to repair.
If I had to fix cracks in one though, I would do it with a two-part epoxy resin, with a fiberglass sheet support on the backside. Bondo makes a good system for this. The space between the upper and lower glareshield surfaces is only 0.75 - 1.0 inches, so it would be tight working in that space.
For the surface finish I used the products below. It turned out great.
adhesion-promoter
vinyl-and-fabric-coating
I used the "Flat Black Vinyl & Fabric Coating", 11 oz. Aerosol, SKU: HVP106, to reduce the glare off the glareshield.
NAPA carries the surface finish products, although they did have to order what I needed.
Rick