Might use a pump up type sprayer. All you want to do is keep the surface wet
with Alodine for 5 to 10 minutes. You could even have it horizontal and do
one side at a time.

The process involves plastic or epoxy-coated rain guttering as a lower
trough,
a series of spray nozzles & black plastic tubing along the upper edge, a
submersible pump, two or three A-frames to support the rain gutter and

thank to both!

Ed