Are you watering well the day before cutting?

Yes, watering well.

How about coolers to rotate through? I stack my coolers behind me, take out a few bunches/bags for display and sell the rest from the cooler. Or, put the cooler on the side and let customers help themselves. Ice beneath the greens in a display bin will help. Don't let the plants touch the ice.

Thanks Robin - any advice for immediately post harvest? Cooling in iced water etc.

I cut as early in the day as possible. If it's hot I dump them by the bushel basket into cold water. If you get them wet you need to be sure to dry them well so that they don't start to spoil quickly.

Thanks Robin - I appreciate your help.

I think the cold watter dunk sounds like a good idea.
After that, keep moist towels over them so the evaporation will help keep them cool and also help keep the greens from drying. Use a spray bottle to "mist" the towels.