My background includes analytical chemistry so I've never shaken off the habit of leaving the laboratory er, darkroom absolutely free of reagent residue. I wash everything, trays, measures, tongs, bottles, sink, tap handles with detergent. Then rinse, dry (clean towels), and put everything away in its proper place. This way I can start the next darkroom session immediately without finding stuff or cleaning stuff. And to absolutely avoid the chance of cross contamination I even wipe light switches and door handles because a trace of fixer here will transfer to hands and cause white fingerprints on every sheet of photographic paper ($$) that gets picked out of the box.