We have a 12 hour stopover at Guangzhou. where can we find a place to rest and shower?

As I know, there is no hourly lounge at the airpport. For the exact information, you can dial
020-36066999 to consult (the hotline of the airport).

If it is true and you are for international transit, you are qualified for 72h visa free policy, you can go out of the airport to have a rest and shower at nearby hotel or hostel.