Well...I assume they aren't foaming sprayers so that isn't an issue then, right, LOL! You seem pretty anti-foam for some reason and if so, could you explain how or if you pre-wash before doing a 2BM?
Test sometime to use your prewash foam in a regualar sprayer. Most solution clinging rather well to be able to desolve the grime and contaminants during the time it needs to be dwelling. Then you will see how much the foam it self is able to desolve the grime and contaminants when not haveing the foam. I have used degreasers that works great without foaming. Sure many times you get a longer dwell time from the foam. And I am a foamcannon man LOL. But a too thick foam can actually be working backwards in the cleaning ability. And it's when it's so thick it won't run off mostly and the foam don't burst or how you describe it. Then you have only bubbles against the surface and that don't cover the surface as a liquid does. Which foam are suposed to do is to desolve into a liquid form slowly and gets a higher dwell time that way. And thicker foam and too thin foams runs off faster. So it's just testing out the right concentration of the prewash foam you use to get the most effective foam.