I've been using those 5lt bottles of distilled water. Mark one with an x and add 1 drop of detergent. Then fill up a dedicated spray bottle also marked x. Warm sunny day on the back lawn tilt scope down to comfortable angle and pack a few towels over the electrics and a bit of cardboard or plastic sheet to drain most of the water onto the grass. Good squirt all over with x bottle paying attention to dirty areas. Then rinse all over another squirt bottle of distilled water only. Finally a few splashes straight from the distilled bottle to final rinse. Let dry last few drops wick off with pointy paper towel.
