I use salt and my standard 2 compartment kitchen sink.
Fill each compartment with halfway up
water. I add about a half a cup of salt to one side, stir it up. Dump the greens into the salt side, let them sit there for a while, 15-20 minutes. I agitate them from time to time.
When I can't stand waiting anymore, I give them some agitation, lift a handful at a time, drop them in the other side. The salt helps irritate and dislodge the bugs. They'll usually float or sink.
Drain the salt sink, refill with fresh water, move the greens from the compartment they are in to this last rinse. In the last rinse they go in for a splash and good shake. Most of the dirt and debris is gone after the salt bath. The 2nd bath does not see much left in the water. If there is a lot of debris, I'll give them another dunking until I'm comfortable with their cleanliness.
Cleaned greens sit in a colander to drain.
I find mulching with
hay, grass and leaves keeps the greens clean. Rain does not splash sand all over the place. I plant a
polyculture so the bugs don't have a large enough environment for their numbers to get out of control.