Mine is an old "GrayMills" washer. It uses a "Little Giant" explosion proof pump but no filters. It has both the soak capability, and the flexible wand for flooding, or a flow through brush. I've had this since the mid 1970's and it's always worked well. I've always used mineral spirits in it but being covered the evaporation rate is very slow. With the use it gets, (and this is often) I probably lose three gallons per year in both evaporation, and what remains on parts that air, or compressed air dry off. I can heat it but usually do not. I snaked a perforated copper tube through the bottom and a constant flow of air to agitate the solvent quickly aids in degreasing parts. Increasing air pressure increases agitation of course for any submerged parts.

I cannot have greasy parts go through my blast line so this is the treatment they receive first as mineral spirits leaves a very clean finished product.  

 Hey Thad,,,that right there sounds like a very workable piece of equipment to have,,,Ya know,,as long as I been shade treeing,,I've never used mineral spirits as the cleaning agent,,,maybe one day,,,,??