i wrap my trays as they have gone thru more than 20yrs of intensive usage by my dad,so those lines in the tray are not dat smooth anymore,i find that wrapping them up reduce scratches almost totally.
i process 120 by holding one end each with my hands and submerged one end into the tray and start pulling up and down each end,something like a pulley system.
advantage of this method is i only use 260ml of soup in a small tray.