Not sure if you still need the answer to this but we checked-in online, dropped bags off at Twilight check-in then just had to go straight to the gate the morning of our flight. No queue at Twilight when we arrived at 6.30ish which is why we bothered dropping the bags then.
Hi- we have done this last year. Yes you check your baggage in at the twilight check-in and get your boarding cards etc, just like normal check-in. the next morning you simply go straight through to security with your hand luggage. it was much less hassle for us to get that bit out of the way the night before as we were travelling long haul with three small children. we stayed in the holiday inn nearby with parking on-site and simply had a hold-all of overnight things which we shoved in the car the next morning before getting on the hoppa bus to the terminal. huh