i basically just ended up wrapping him up in his blanket, feeding him to sleep in my rocking chair while my toddler played on the ground in front of me/watched a dvd, then placing ds2 in his cot. the first few months he would only sleep for about 40 mins, but now that he has grown up a little, he'll do much longer sleeps- yesterday he slept for 3.5 hours in the day. i didn't do anything different to make this happen, i think it just happens with maturity tbh.
part of your battle is teaching your toddler to be quiet whilst you're settling the baby. i did this by putting his fav dvd on for 10mins or so whilst i was settling ds2. he then knew he had to sit and watch it quietly and it was a bit of a treat for him iykwim? then once the baby was in the cot we would spend one-on-one time together so it was win/win for ds1.
good luck and hang in there, it does all get a lot easier once they hit 4 months, i promise!

eta- have you got a sling? i nearly wore a hole in my hab i used it sooooo much when ds2 was a baby.