Wow, it feels good to know that i'm not the only one who has this problem!
my older ds 3.5, rocked to sleep till he was around 3. younger ds (11 month baby) was born when older ds was 2.5, so i had to gradually 'wean' him of rocking so that i could take care of the baby. still, many evenings, i would be cuddled with both of them in the rocking chair... gradually going to sleep.
Older ds is now beginning to be able to fall asleep on the bed; he's realizing that the rocking chair just doesn't have room for all of us, and it's more comfortable on the bed. Also, both boys just end up playing on the rocking chair instead of going to sleep... and that can be frustrating sometimes.
Sorry... now your question.
With older ds, for trips i would also be so worried, but then just ended up walking with him in the sling... or swaying and rocking while holding him. It did take longer... but it would definitely work. As he got bigger and heavier, we started using the stroller; or just waiting until he was sooo tired that he would go to sleep as soon as he started nursing.
With the baby, we just went to in laws house for memorial day weekend. It was rough; he was awake, climbing around until 1 or 2 AM and i was just too tired to walk him to sleep. i would walk and sway, but then sit down cuz i was falling asleep. All my friends' comments about how crazy it is to have to rock them to sleep were just going through my head. it was rough.
anyhow, it's good to know i'm not alone! It just seems to be harder for me to lie down and put the kids to sleep; especially when they just climb all around the bed and i have to pretend to be fast asleep. it's easier to rock in the rocking chair, nurse, and read MDC!