Use trash bags
What you want to use are the white non-scented kitchen trash bags. Black trash bags work OK, too, but you can't see through them as well. Lay down the first piece of plastic on a smooth workbench. Place however many layers of fiberglass you want (four is my limit), cut oversize, on the plastic in the proper orientation. Pour on the epoxy and spread it around with your 6" Thalco rubber squeegee. Wait a few minutes while the epoxy penetrates all layers (use a hair dryer to speed up that process). Squeegee off the excess epoxy being careful not to disrupt or pull the weave of the cloth. I use a tongue depressor to scrape the excess epoxy off the squeegee and back into the mixing cup.
When you've removed all the excess epoxy from the cloth, apply the second sheet of plastic on the top. Use a "pizza cutter" (available from ACS) to cut the sandwich to the desired size and shape. Remove the bottom layer of plastic and apply the fiberglass to the prepared workpiece. Use paper towels to remove any air bubbles and smooth out the cloth. Peel off the top piece of plastic and use a 1" chip brush (cut on an angle) to stipple out any remaining air bubbles. Apply peel ply in areas where you will be bonding something else to the top surface or where you want a feathered edge. (Keep in mind that using peel ply adds weight.) Clean up your tools and gloves with Acetone.
Safety note: Wear Butyl rubber gloves with cotton liners during this process.