For years we would clean the hundreds of queen excluders by the above mentioned methods. :-\
For some reason one year they did not get cleaned.
To find out it didn't matter there was no more wax on them then when they where installed. Since then the excluders get a quick scraping so they store and sit flat, THAT"S IT!
The bees seem to want to put/fill a certain amount of wax on them , but never do they come close to sealing them up