Schedules are hard to find in the Philippines and are not always reliable. Ceres Bus liner, the biggest in the country, provides regular buses between almost every city and barangay in the Philippines.
The point is to find the right and most comfortable bus. Going by a regular bus can be a fun experience and you meet a lot of locals. Windows open, chickens on board. But also a stop at every corner and little to no comfort.
In between the bigger cities, there are air-con buses riding back and forth. They offer more comfort, there is a video on board for entertainment and many offer free wifi. Some even have onboard CR.
There is not much price difference between liners and local buses. So if you travel a long distance, maybe an air-con bus is a good option.
Cost breakdown stops, and the rest of the route between Dumaguete and Cebu you can find in this post
Time tables aircon buses between Dumaguete and Cebu and v.v.: