I’ve done the oxalic acid bath thing previously. I used half of a cardboard box, sized for the frame, and lined it with heavy duty plastic. A problem was what do to with that “tub” once the process was complete. It was too heavy to lift and dump in the sink; too low to siphon. I think this time I’ll use a smaller container and go one tube at a time or try the soaked paper towels wrapped in Saran method.