I do the pump sprayer with ONR and some car soap...I have not yet had an issue with a grime layer hanging on after the clean rinse...but this is the first truck I've ever had such a kept-up layer of LSP, also. I will never again use the coin-op soap or pre-rinse. It's too harsh and I no longer see the need...and it only takes 4 quarters worth of clean water to do what I need done, even on my big truck. I even gave up on the spot free rinse since I can be home in 5 minutes to do the drydown. Maybe in below freezing weather I'll change my mind.
I always come straight home and follow up with a QD strength ONR wipedown/drydown as well.