My food is pre-prepared in individual servings in freezer (if hot) or sandwich (if cold) bags. I add water to the bag (hot or cold, depending on food), let it sit (in a cozy if hot food) and eat out of the bag. This is the freezer bag "cooking" method on www.trailcooking.com, "Sarbar's" website.

Yes, all your food should be kept together in your food bag or bear canister; just keep out your snacks/lunch for the day.

Some prefer to take bulk ingredients and do their cooking in camp. IMHO, this takes longer, requires more fuel and involves pot scrubbing. I hate washing dishes! This method, of course, uses less plastic bags.

Your Mileage May Vary!