I spray baste mine on top of my double bed. My knees and back just can't handle getting down on the floor anymore.
I've only used June Tailor and 505. Love the 505 but it sure is expensive. I buy it when I can.
I get an old king size flat sheet that I bought from a resale shop and cover my mattress with it (I take my blanket and sheets off so I can just use the mattress).
I can pin the quilt layers taught onto my mattress as I spray and assemble.
I've seen a video of someone covering a wall with newspaper or painters drop cloth, and taping the backing to it, spraying it, pressing the batting to it, spraying it, then pressing the quilt to it....all vertically.
Next time I'm going to try that.