Re: best medium for cleaning swarm traps?
Shake the loose stuff out..
Then - propane torch them inside.
Burns off the small crap.
Melts and distributes evenly the large crap across the surface (good for a trap; I would even add old wax/propolis mix and melt it inside, while at it - for a better smelling trap).
Don't bother scraping/washing/whatever...
Unless bored and have lots of time to kill.
The torch - $20 from HF (plus camping propane tanks).
Former "smoker boy". Classic, square 12 frame Dadants >> Long hive/Short frame/chemical-free experimentations.