We’ve been doing some research into air knives and considering ways to make staining of thousands of small parts faster.  Dip it into the stain, and have a captive air knife blow the excess off (dripping back into the bucket) as the part is pulled out.

The PVC tube will be hinged so it can be opened for cleaning.  The air knife assembly will be near the top of the tube.

Did some checking on PVC compatibility with stain and it seems to be acceptable: https://www.berlinpackaging.com/insights/chemical-guidelines-for-plastic/

Here is a possible air knife kit. http://www.exair.com/index.php/products/air-wipes/super-air-wipe/saw-kit.html

Now just need to design the servo motor mounts, air knife mount, and misc. other structural components.