Deck sealer application
If you don't need to clean and reseal the deck to start with, you can use a wasp/hornet/flying insect killer in a spray can.  They usually shoot a stream at least 10 feet so you can single out the holes and get the bees as they fall out.  Fill the holes with caulk afterward so anything left inside can't get out.

If you plan to clean and reseal the deck anyway, a pressure washer does fine for cleaning but would have too much splatter and overspray for sealing.  Try a roller on a pole or a garden sprayer with a long nozzle so you have better control applying the sealer.