I'm not laughing about the hose & pebble setup - I have similar contraptions for washing prints! I also prefer flat-bottomed trays for the same reasons, plus if you tone in a ribbed tray, the toning tends to be uneven due to the flow patterns across the ribs unless you use an enormous volume of toner, which is uneconomical in the case of e.g. gold toner.
What gold toner recipe are you using, or is this a commercial preparation?
That's a fine print; very nice indeed.