I really wanted some inexpensive surfaces to practice painting on, really cheap so that I wouldn't be afraid to 'mess up' but durable enough so that should something actually be good, I could give it away or sell it.
I did some research and found many people paint on Masonite, so I went to Home Depot and got some Eucatile Diamond White Tile Board. The white coating is glossy so I'll sand it a bit with 400-grit sandpaper to rough it up and gesso it, maybe front and back for safety's sake, masonite and moisture are not friends.
The nice gentleman in this photo cut the 4'x8' panel into quarters. When I saw how nice and clean the cuts were, I asked Don, "We do have a plywood blade for the table saw, right?". Ah, no. So I asked the guy and offered to pay for additional cuts to make 32 12"x12" panels. He said he'd do it gratis, and I'm grateful.
Now to sand the edges and prepare them to paint.