Have you ever thought about setting up a motorized scratch brush? If so, take a look at mine:
Used primarily for cleaning and burnishing metal. The lower translucent tubing supplies water. Should the piece require the help of a detergent, the upper tubing is connected a valve attached to a HDPE gallon jug containing 100% plant-based dish soap. It’s a gravity-fed system. A crimped nickel wire goblet brush is attached to the extension arm which was made at a machine shop. The translucent tubing to the left of the image is attached to 1/2" copper tubing via a saddle valve. I attached shrink tubing to the shaft to eliminate scratching in deep objects. The motor runs at 1750 rpm with a shaft pulley of 1" which belt-drives a 3" pulley = 583 rpm.