At the risk of being bashed by KF -----------the house painters here use retarder all summer in their w/b acrylic house paint, and I will bet my lefty that what they use in W/B is PVA glue. It looks like it, smells like it, and sticks like it, so mix a bit with a blob of water, then mix it with your paint and see what happens, I know it makes paint flow off a brush / roller like oil, and this is what you want when spraying, not a heap of microscopic dry hard bumps. I might have to get my microscope out and take some pictures***##@@@!!!.
I'm solely here to save you money .pete