It takes about 20-30 minutes from Macau Airport to the Barrer Gate and about half a hout to get throught he custome of Gongbei Port. Then you are in Zhuhai. It takes 3 hours from Zhuuhai to Shenzhen Luohu by bus and pass the border to enter Hong Kong. Another 20-30 minutes by mtr from Luohu to Mongkok. To be faster, I suggest you go to Zhuhai Jiuzhou Port Ferry Terminal to take ship to China Ferry Terminal in Tsim Sha Tsui (70 minutes). Then take bus to Mongkok.