We had a soft bodied but plastic limbed doll around that age. It was light enough for DD to carry as some of the all plastic ones can. be heavy. Think ours was from ELC.
We had an Usborne book about “The New Baby” that was very simple and clear. About mummy going to hospital, visiting them there and new baby coming home.
We never stopped older siblings touching the baby but we always encouraged them to stroke their legs and feet. This kept them away from their face.
We also put a baby gate on the main living area and baby proofed it. So that when I was feeding I had less to worry about as the toddler was contained. Also all their toys were in the same room as us.
Another thing that I was told that sounds a bit strange is if you are doing something for the toddler eg. getting it a snack or drink, something quick - don’t immediately stop it if the baby cries. If the baby cries for 30 secs or 60 secs it won’t know but your toddler will quickly notice if it gets ditched every time the baby starts crying.
Have a change mat and basket (with nappies, wipes, vests, babygro etc) in the main area the toddler spends time. I only ever went upstairs to use the proper change table for DC1.
All mine were around 2 when the next one arrived. The toddler always enjoyed guessing if the baby had done a wee or a poo when the baby needed its nappy changed.