That is an excellent and effective way, and also an economical way, to clean bacteria from your hands. People also need to be careful about the water they drink. Lowry advises bringing purified water from home. You shouldn't consume water from lakes and streams unless it has been boiled or treated with water purification tablets. After the meal, be careful about deciding what to take back home with you.
Leftover food is only safe if there is still ice in the cooler.
Most recommendations are just common sense. Most people don't get sick from picnic food. As long as you're careful about how you handle your food, your summer camp outs, picnics and barbecues can be just as idyllic as you imagine.