What I find helps is working out all the carbs for a new meal, doing the insulin thing, test before, then one hour after, two hours after then three. Because I'm really boring I'd eat the same thing again the next night but adjusting then testing. I then get closer and closer til I've nailed it with the insulin.
Might be a bit difficult to eat the takeaway every night though. ( I wish!) But if you eat the same meal every time you order by testing you'll be able to get closer and closer to the dose.
Some of the set meals at home that I eat I don't carb count now because the same things are going on. So I know 2 units for a green salad with 1 unit an hour later for the chicken.
Do you know if your basal (background) insulin is right yet? This can have an affect too. But once that is sorted then you are bolusing for food rather than having to deal with using the bolus to correct and deal with the meal.