Hello twin mommy! I feel like I am always working through new sleep issues with my now 13 month old twins and have a few thoughts.
I nap them in separate rooms (DD in nursery, DS in p-n-p in my room) which helps a lot - otherwise they "talk around" and never go to sleep. Different story at night, they sleep in their room together.
Up until TODAY (God help me) I used to put one of them in their infant swing with a bottle while I rocked the other in the room with bottle. Then I'd get the other, rock them to finish the bottle and then put down. I never let them fall asleep in my arms, always put them in their crib drowsy.
When we began the bottle weaning process about a month ago, I would do the same thing minus the bottle. This greatly shortened the mama time in the rocker (clearly my issue, not theirs) but they still went down just as well.
We decided this weekend it was time to let go of the swing-crutch, so this morning I got them both upstairs, read them a book in their nursery, put DD in her crib and then DS in my room and listened to my DS cry for about 3 minutes, and my DD is still crying/whining a 1/2 hour later! However, she is a very determined and stubborn little girl and is starting to get ready for one long nap, so that is probably her issue (I still need my morning shower and am trying to keep them on the same schedule, so wish me luck).
I'll be honest, it is not easy on your own and you'll miss holding them after they eat on the way to their nap, but it really will work and the crying really doesn't last very long after the first day or two. If you stick with it, you'll find that almost immediately after you leave the room they quiet down and fall asleep. What a wonderful feeling it is!
One thing I read by Dr. Weissbluth that really helps me in these transition times, is that you are teaching your children to sleep well which is so important for them for a lifetime. You are certainly not hurting them by a little crying (which always FEELS like a lot!) and this too will pass and your little angels will be happily snoozing off on their own sooner than you think if you stick with it.
Now, I am not a childcare professional or a doctor by any means, but I am a first time, somewhat neurotic 30-something mother of twins and, although books and advice do help, I have found that by rolling up my proverbial sleeves and doing the hard work for a couple days (listening to babies cry, missing the old experiences with them) I am ultimately most successful.
Best wishes mommy, listen to your instincts, hang in there and your twins will soon be independent snoozing little angels.
H.