It depends.

I have a few things to say about this but it may be a short while before I can reply in a detailed enough manner for it to be remotely useful.

I'll try to make a video reply later tonight.

As of 6:37 PM ET, nada

Crap! Sorry about that. I will re-upload this tonight as something must've gone wrong. I should have this up in a couple hours

And here's the kicker about just scanning and going.

Manufacturer's change the makeup, serving size, macros and calories in a product all the time, some more than others.

The SKU will stay the same usually.

Guess who doesn't update their database entry that is tied to the SKU. At least I stopped checking once I saw how bad it got. Perhaps they eventually do.

I'll mention this process, only because it can be made more difficult, or easier. Still sounds difficult until you do it with scratch paper on your counter.

Stuff like chili not too bad - you got the cans and spices don't have calories to speak of in quantities you'll be consuming. While some cans are in volume of ounces rather than weight of ounces - you weigh it once you got it - make a note somewhere.

Here's how you do it, if you keep the recipe and especially in MFP, you got the info.
Weigh the pot it will end up in, hopefully not over what the scale can handle. Note that. Say 2 lbs, 32 oz, 907 g.
Add your ingredients, weighing what's needed, don't worry about water added. Note all those weights per item.
Cook as needed.
Weigh the pot now, do the math for weight of food. Say total 4.5 lbs, 72 oz, 2041 g. Food is 1134 g.
Weigh out the portion of food you want to eat, that appears will satisfy you - say 284 g.
284 / 1134 = 25% of food eaten, which also means 25% every item total eaten.

Build a recipe on MFP so you can do this easily again.
When you put in the ingredients that have calories, do NOT trust the "about XX servings per container" - do the math on those parts, can product weighed 170 g (stated or you weighed), serving size was 50 g stated on can, use 3.4 servings used in recipe builder.
Now whatever weight it comes up with doesn't matter, you know you had 25% of it. You can mess with the # of servings to equal some even amount, you can make it match what you ate, whatever.
Eat some leftover tomorrow, same simple math process - say 200 g / 1134 g = 18%.
If you made a serving equal the initial 284 g, then 200 / 284 = 70% of your serving size you decided.

You do this with a batch of common recipes that is mostly eaten, especially potentially high calorie ones, and the others that may be created can be estimated with something already in the database.
Sort of half what Patrick was talking about, half more accurate.
Doesn't have to be all or nothing.