I use a combination of gutter troughs, dog feed bowls, and rubber bowls. The gutter troughs I made have a spinning dowel on the top to help keep the birds from standing on top or in the feed.
As for washing the feed bowls/troughs: I do so quite infrequently, or only if they are really gross, or if they have been pooped in... (guessing poop fits under the really gross heading!) Then, all I do is hose them out. IMO, any little granules of feed left from yesterday are inoculated with the SCOBY, so will continue to help the feed that I put out today to continue it's ferment.
As for washing the feed bowls/troughs: I do so quite infrequently, or only if they are really gross, or if they have been pooped in... (guessing poop fits under the really gross heading!) Then, all I do is hose them out. IMO, any little granules of feed left from yesterday are inoculated with the SCOBY, so will continue to help the feed that I put out today to continue it's ferment.