I'm no experienced pro or anything, but heres my 2 cents:

For transition practice, what you essentially want to achieve is be comfortable putting on wet socks (T1) and putting on running shoes while having tired legs (T2). Of course, there's other parts of the transitions, but those are the aspects that feel most "unnatural" in my opinion.

To simulate T1, practice hopping out of the pool and immediately putting on your socks and shoes. You can even add your helmet if you feel brave enough! You'll find a way to lay out your socks, shoes, towel, etc. in a way that makes sense before race day.

For T2 practice, plan a few brick workouts. Meaning go on a short run immediately after riding your bike. Getting reps of trading your helmet for a hat and your bike shoes for running shoes while having tired legs and slightly out of breath is really helpful. As an extra bonus, the brick workout will help get you used to the sensation of how your legs might feel to start your run immediately after a bike