Make a grit board - Take a file folder and glue a sheet of very fine grit sandpaper on to the folder. Have the folks that are signing the blocks place the fabric on the grit board - it helps hold the fabric in place while they sign the squares. Be sure that the sandpaper is a fine grit. I took a piece of fabric to the hardware store and tried out the different sandpapers. It is also important to draw a border on the edges of the fabric - people signing don't understand the whole concept of "seam allowances". I had the signers use Pigma fine tip markers. This quilt was for a co-worker that retired - I ended up with 84 signature blocks. Good luck with your project - I think you are doing a wonderful thing.