Honestly, I spray on my bed in bedroom. I have a California King and I've been able to do every size quilt that I make. Though, I do use my Joann's cutting table for small sizes. I remove the pillows and cover with a very thick cover, like a moving blanket type of thing and then I cover that with an old thick sheet and tuck in so that every area is covered and protected. I think lay my backing out and very gently and ever so slightly stretch it out and secure it with T-pins. I spray close to the fabric so I have not had any issues with overspray at all.
If it is a calm day I open the window. I use 505 exclusively and I do not find it as fumey as some of the other brands.