For leaf lettuce I always washed it, spin dry(you do have a salad spinner right?), then wrap in barely damp paper towels and place it in a ziplock. Would keep 2 weeks easy if I got away from my normal salad a night routine.
Start here http://nchfp.uga.edu/how/freeze.html I blanch and freeze a lot of garden produce. Blanching times depend on what it is so go by the guide. I vacuum bag mine and have had 3 year old veg that still tasted fresh picked.
Get a 5 gallon water cooler like you see on work sites. Fill with as hot of water as you can but NOT boiling(plastic is not designed for 200 degrees!) When I catered that was what I used. Could run it to the house on site or refill by hot water off a camp stove. Has a spout to fill a small plastic tub for hand washing.
And bring a box of gloves! I used gloves a lot, saved on needing to wash hands constantly when prepping 200 pounds of meat. I could prep everything, get...