Working out carbs can be a pain but the more you do it the easier it will get. Once you know how much carb is in a sandwich for example that will not change.
Buy an address book, one with letters down the side. You can then record the food under the correct letter with the amount of carbs beside it and use it to refer to when you need it.
Carbs and Cals is also a good book as you have pictures of foods with portion sizes and the amount of carb per serving.
It is all a pain in the backside but you will get used to it.
Good luck x