I just cleaned mine. I don't use it much anymore, it had been a long time and had evap to the point that it didn't ****. I fill it full. the bottom had rusted some minor pits so I cleaned it and painted it, filled the edges with about a quart of white Imron.
Any way, I added a ring that just sits over the factory suction screen, its kind of a **** design. Igot a tray or 2 can wash gook in to and dispose of super dirty if I want and I also put a valve on the pump drain so it could be cleaned a little easier.
If you use it a fair amount can pump it off in 5 gallon pails, right thru its own pump, then clean it out and add more fluid. It cost me about $200 or so but mine is near sterile again. Eventually when it gets low I pump another gallon in, can run it from full down to about 5 gallons before it doesn't work and by the time that's done its pretty grimy.
But,,, a big thing is to pre clean. I wipe and scrape first, if I can put a gob of grease away in the trach with a paper towel I do it. Second, not all have this but I got a hi pressure hot washer. While it seems like a huge expense,,, like a good garden tractor or so a 5 grand machine earns its way, worth a payment, lasts way beyond the payment and saves so much super hard work along the way that a busy guy could easily make it pay keeping equipment nice and reducing depreciation in many cases.
I also moved the bottom shelf up am inch or 2 to fit the pallet jack, guy could add another one too.