FYI: Silicon-Carbide Sandpaper Source
In my own quest for affordable supplies, I've been combing the Internet for sandpaper sources -- as the SRP Wiki teaches, I searched for silicon carbide sandpaper that can be used wet or dry. Without exception, they're either selling 5- or 10-sheet packages of single-grit 9"x11" sheets (or smaller! often, half- or quarter-sheets) for $10 or more, or an "assortment" of four-or-five different grits (one sheet, each), in small sizes, for $10. Phooey! and not on my poor-man's budget. Then, I found this offering, on eBay:
25 Sheets Sandpaper WET DRY 9x11 Sand Paper any grit 150-2500 Silicon Carbide
For all of $13.50 + $6 S/H
As that satellite-TV ad goes, "I jump in it!"