Depends on the budget. If you have lots of luggage, and want point to point, something like
Asia Car Service will pick you up from wherever and drop you at the airport. Depending on how the wind is blowing / what changes have happened, have had both just sit in the car as you go through customs / immi back into Hong Kong (IIRC in the car back to HGK is normal) to get out and lug your luggage through the queues (but I think this is more going into China - but have had both).
Definitely hassle free - but far from cheap (just depends how much stuff you have to lug). I think around US$220 - makes more economic sense with mutlipe pax.