[6510]

do it outside or spray water into it

[teraku]

This. I use a bag free (manual) vacuum and I even though I can manage it without water and not create too much airborne dust, if you just spray water it slightly it will stick to eachother and become big balls.

[rini17]

Doing it outside already.

There is also paper hepa filter on it that can't get wet. Even so, not sure if mucking with dirty water is worth it.

[6510]

There is also the silly solution: Empty it while holding the nozzle of a vacuum cleaner nearby.