Step 1: Food-grade pickle buckets
I regularly visit a nearby chain burger joint, and its manager has his buckets rinsed and set aside for me to pick up when I drop by. I offer them free to friends and neighbors and to a charity that helps local folks. You could do the same in your neighborhood, or just get a few for yourself. Bakeries, donut shops and the cake departments of grocery stores also get ingredients in buckets, and they are all much easier to clean than buckets used to ship paint and drywall compound.