Zhuhai is only two hours drive from Guangzhou, I don't think there is toilet facilities in the bus. You can find bus at Gongbei Bus Staton and Xiangzhou BUs Station. The bus usually stops at Guangzhou Railway Station or East Railway, Tianhe Bus Station, etc. You still need to take a taxi or other public transportation to the hotel by your own.
For the bus to Shenzhen, you can get the bus station nearby Guangzhou Railway Station. They are easy to found.