Hi Sam -- I've had very good success overall with Behlens line of
products.  They can be obtained by mail-order from most of the major
woodworking supply outfits (Woodcraft, Garret Wade, Lee Valley, etc.).
For addresses, phone numbers and web sites see
  http://www.cs.uu.nl/wais/html/na-dir/woodworking/addresses/list.html

While the orange flakes will probably work fine for this application,
once you experience the pleasure of working with fresh shellac you'll
probably start using it for lots of other finishing tasks, so I'd
suggest springing for the extra couple of bucks to go to the blonde or
super blonde grade.  (For small projects a pound lasts a long time!)

I've mostly used their proprietary solvent as well, not trusting
what might be in the denatured alcohol from the Home Square Quarters
Builders Depot.  Lab grade absolute ethanol works fine as well and
is less toxic, but it's harder to get.

I have to admit that I've almost never mixed exact proportions.
Dumping flakes into a jar and adding solvent to just cover seems
to give a cut that works well for all sorts of sealing (under other
finishes) and finishing applications.  The experts at MMD will un-
doubtedly give you better advice on the optimum for this particular
use.

Cheers!

Roger Wiegand