you'll need to buy the (one-way) ticket online and they will send you 2 booking references (seperately, for the "bought" one and the "free" one). Note you'll need to check the relevant boxes when buying the ticket with those VI to earn the free ticket.

you'll then need to redeem the tickets (with the above references) just before getting thru the gates. (so just as you board/ITCI when airport-bound, or after you get out of the train in town when city-bound)

you could also redeem in the airport for city-bound trips before you board the train.

tommy14, im thinking with 30 ppl you might be better off to charter a coach for airport-town trip at a lower cost. otherwise if you're heading to HK station i might be able to give you guys a hand since i only have to buy the ticket just before you guys get thru the gates.

SirJman you'll need to be getting the 1-way ticket. not the travel pass.

Clipper801 as mentioned above you wont even get thru the purchasing process if you dont use a qualified VI. "showing the card" is just to verify you being the holder of the booking. otherwise you'll have an authorization form.