Err.. can try my method la if you think is useful. Use a plastic bag cover your hand and feel the surface. If you feel there is something on on the surface then need to clay. I use ONR as lubricant. Never tried got marring when I have a clean surface to clay. Only got a few hair line before cause I think I picked up some tiny hard object then when wanna inspect the paint only I know I screw up from the preparation. I tried use opc to clay before and then end up my claybar melted. That's why I ask you how come your claybar wont spoil.
I clay left right up down, then wipe dry with a damp mf to feel is there is any pokey pockey feeling on the surface. If you not use to check contaminants with damp mf then use plastic bags.
What was your concentration for ONR and OPC? My OPC was super mild, 1 part to 10 parts water. ONR I'm doing 50-50



