I have a difficult time getting down on the floor, but I spray baste even king & queen size with 505. I do it in the garage with the door open and a plastic painter sheet taped down on the floor. It helps to have a second pair of hands, I have my husband help me. I lay the batting down first, place the backing on and smooth first with my hands and then with an old 24 x 6" ruler (softly). Once that looks good, I pull back to the mid-point and spray lightly approx. 2 ft x width and with one of us on each side, slowly settle the quilt down flat & smooth out, repeat til you get to the end and do the same with the top. I let the glue set for a few minutes and carefully turn the quilt over and repeat for the front. It makes fmq a breeze!
I do wear latex gloves to protect my acrylic nails, that stuff does not come off of acrylic (rulers either) except with solvents.