I have a friend, who with my help (breastfeeding counsellor) we managed to drop all the top-ups over a few weeks.
Firstly it will be much easier if you are tandem feeding. You don't mention whether you are or not, but I would highly recommend it! Get a good cushion, the EZ-2-Nurse inflatable is good. Latch the more difficult feeder on first, then the better feeder. make sure they are wrapped right around your body and quite far back so they start nose-to-nipple otherwise you'll get sore.
I would start with one of the morning feeds as Mums tend to have LOADS of milk in the morning. Basically the breast works on a supply and demand basis, the more often a baby is latched onto it, the more milk it will produce. Breastfeed them both, don't top them up, just put them back on the breast 5-10 mins later and you will get another let down of milk. If they still don't settle, put them on again, etc etc! Eventually they will have had enough. Continue with other top-ups as before (unless you're feeling brave, you could try more than one feed!). Do this for 2 or 3 days to let your milk supply catch up and you should find that they settle much easier, then drop another top-up. Keep going until you have dropped all the bottles. I would leave the evening ones until last as babies are always grumpy in the evening. You should find that as your milk supply increases, night-time bottles should be quite easy to drop.
I would refrain from expressing until after you have dropped at least the morning bottles completely as this is the best time express. You don't actually need to express though as you can give it directly to the babies... soooo much easier!
Good luck.
Do you have any breastfeeding drop-in groups, or breastfeeding counsellors in your area? Or any other twin Mums who have breastfed? Be worth making some contacts and go along to a postnatal or breastfeeding group.