Add 1 cup (~200ml) of washing soda powder to your favorite laundry detergent. Use washing soda, not to be confused with baking soda. Washing soda has a higher PH. That helps dissolve the propolis and run it down the drain.
Washing soda is also great for cleaning tools, fill a deep tray with hot water, add a bit of dishwashing soap and then add washing soda until no more will dissolve, and then soak your tools, excluders, whatever in it. After a while wipe and rinse clean. Sometimes thick propolis on items like excluders will need a resoak. Warning: This will take paint off of items such as hive tools.