@aart yeah, basically oilcloth is a heavy canvas that's waterproofed on one side. It's much heavier and sturdier than a tarp, and pretty stiff - doesn't drape like a tarp, but sticks out stiff. That's why I was thinking it might work for this purpose. The reason why I thought of it at all is because my mom and grandma used it when I was growing up, instead of a regular tablecloth on the table, because it's easier to clean up - just wipes clean, as opposed to having to wash a stained tablecloth in the washer. That's its main purpose, I think. Why they needed to use anything at all, I don't know. In my house now I just have a regular wooden table with nothing else on it. Wipes clean just fine, even with little kids making a mess... and it looks nicer, too. But I guess that was a thing back then.
I'll need to think about this some more. Maybe I'll use blackjack 57... I just wanted to shave off unnecessary expenses, since I'm already buying most of the materials new. I already have a roll of oilcloth for another project, and I'll probably have enough leftover to cover the coop floor as well, so I might just give it a shot, and if it rips too much, I'll take it out and paint blackjack next year when I do my first full clean-out. I'll only be doing the big clean in warm weather, to avoid cracking anything, and I'll use plastic tools to scoop and rake the litter. Now that I think about this some more, I actually want to use kid size tools. They're smaller and easier to work with in the confined space of the coop, and they're usually plastic. My kids have some reeeeeally convenient-looking little snow shovels and leaf rakes... I won't steal them (probably) but I bet the kids will get a kick out of having the chickens "use" kid tools just like theirs
P.S. I'm designing everything so I won't have to scoop and lift when deep cleaning time comes around. I'll have a floor-level opening on the back wall, with the compost pile on the other side of it just outside the chicken coop. That way I can open the "poop door", and just push everything out and onto the compost pile. I might be able to do that with a push broom, which would be even gentler on the flooring.