Normally, you can ask for a special resealable bag at the duty shops and it should be fine. I bought some perfume (over 100mL) from SYD, transit via HKG to Beijing, HKG airport allowed me to go up to the departure level at the transit area (did not go through immigration) without confiscating it because it was in the bag with the receipt inside.

However, this does not work if you are flying to Australia. The problem is that Australian government does not allow any liquid over 100mL to be brought onto the aircraft at all, plus there is another check of hand baggages inside the gate (after they scanned your boarding pass, before you board your flight, so you cannot buy any liquid over 100mL at HKG airport).

Solution: enter HKG (i.e. stamp on your passport) and go up one level to the departure area, head to the check-in counter and check-in your liquor or whatever liquid over 100mL.

This is exactly what we did before. I flew from Osaka to Sydney via Hong Kong with a friend, she bought some cosmetics in Osaka airport, and while transit, the custom officers at the transit area told her that she cannot bring them, and told her to check them as check-in baggage.