First off, I'd like to mention I'm not a trainer (SM won't let me bc favouritism and I dont like small talk w customers) anyways. I had an awesome pod trainer and depending on where you're training, have each person watch and try it themselves.
Steaming milks as you know, 1-3 secs lattes, 6-8 cappacinos. Groom the milk etc. Show them slowly how to do it, have them practice, then show them how to sequence, have them practice one by one in the group. Take pictures, compare.
For POS, group things together to make it easier to remember, have them practice taking each others orders. Have one go around as a customer, teach them how they're supposed to talk to customers while ringing in an order. Have some of them act like friendly customers who want to chat and have some not be as talkative so they have an idea of how to tackle both general groups.
Show them how to connect over bar and at MOP.
You're a trainer so you know starbucks emphasizes customer connects so have them make a drink and talk to a "customer" in the cafe.
One thing I wish I had was a chart and a better explanation of pumps and shots, mainly with less made drinks like how the HCM gets 2 pumps of syrup in a V and G. Flat whites dont come with blonde shots by standard but get an extra shot, same with americanos. machiatos get one less pump of syrup. Matcha frap gets half pumps of classic but strawberries and creame gets full pumps. Those kinds of drinks stumped me for the longest time so go over those (surprisingly not a lot of people do).
You've got this.