Put eye hooks on the outside of doors at the top, so that you can keep the toddler out of rooms when you are tied up with the baby (they can easily be ripped out in an emergency)
Have a safe spot to put the baby on each floor of your house where the toddler cant get to them (or ‘give’ them toys) so you can nip to the loo/answer the door
Always blame yourself and not the baby for not being able to do things. So if toddler wants to play and you are feeding, say Mum just need to sit down for a bit as my legs are tired, not the baby needs a feed. That helps to minimize the toddlers jealousy/frustration with the baby
Go overboard on how the toddler has a brother/baby and how much the baby loves the toddler. “Look how baby is watching you, thats because he loves you so much”. “Oh my goodness toddler, you are babies favorite, see how he is waving at you”
Tell toddler that babies like their toes kissed and tickled, it keeps them away from the babies head.
Some days will be good and some days will be awful. Try and see each new day as a new beginning for everyone
Really try and have both dc in a routine asap, its the best way for you to have some downtime. I remember almost crying with relief when I got mine napping at the same time after lunch. I had 2 blissful hours to quickly nap myself and then prep dinner before the crazy started again
Get the toddlers bedtime routine to a minimum before the baby arrives.