Tips for moving 15/16m old from crib to twin size bed (with rails)?

Hi all - looking for tips on moving a younger toddler out of a crib.

for a variety of reasons we will be graduating our 15/16m old from his crib into a low twin bed (with rails) very soon. He’s 15m now but when he’s 18m his little brother will arrive and soon after will be sleeping in the crib in the same room. We don’t want to buy another crib since the older one is already close to climbing out, he’s tall and strong for his age and he’s a climber so feels like a waste of money to use only a short time.

We will be making the nursery fully baby proofed with a baby gate at the door so he can’t roam around if he gets out of bed. And it’s a small room so likely will just be a crib, twin bed and chair. No toys or activities.

I’ve been told to move him sooner rather than later so he has time to adjust before baby bro arrives and his world changes again.

He’s a good sleeper and we have a fairly simple bedtime routine. So hopefully that part goes well.

Any tips you found helpful while transitioning?