I use a couple 4' x 6' pieces of cheap carpet from Home Depot- kinda like the outdoor carpet but softer. The edges unravel when you cut it into sections so I use a torch to go around and melt the edges. I bought a 12' x 12' piece and made those 2 plus 2 smaller ones I can use for throwing down to do things like set up a floor jack or work on wheels or doors so I don't have to kneel on concrete. The stuff if thin enough and lays flat enough that if you do decide to use a creeper, you can roll easily on it and even roll completely off and back on without the wheels catching it but still thick enough to help. I just did the transmission in my 02 AWD and I'm 60 with back issues. It really helped.