When I first got my longarm and discovered the 4 pole system, I fell in love! I don't use any sprays, as I'd never want that on my frame or machine. And I don't find it necessary, just an added expense/step.
When floating, I don't use anything either - if it's necessary, then I'll insert 4 or so pins in front of the top bar to hold the layers still, but otherwise, usually the batting will hold everything just fine. If you find your top is scooting, then your machine foot may be too low and moving the fabric or you may be working with an extra fluffy batt (that does call for more pins). Or it could be the quilt is being rolled too tightly (it should only be tight enough to pull the wrinkles out, not any tighter as that leads to needle flexing and stitching problems). Anyway, if it's needed I will pin down my sides, but since I always baste them down, I hardly ever pin. The basting holds them well for going off and on, and it sure helps with the binding as well. My folks love that I baste the edges for them.
I've tried every method on the market the past few years since I got my machine, and this the one that works best, and fastest for me ;)
Just the way I do it...
Debbie in Austin