International-International Transit for 8hours at Guangzhou Airport.

For your 8h layover, you don't need a visa. If wanting to leave the airport, you can directly apply for a stay permit at the customs. I suggest you take subway (line 3 to Jiahewanggang, then transfer to line 2) to Haizhu Square within 40-45min. Roam around the square for shopping, have a look at the view of Pearl River, then walk to Beijing Road for more shopping and dining. After, take a taxi or subway back to CAN. Seize your time and it is suggested to get back to the airoprt at least two hours before the flight schedule.