Hello, as Galteemore suggested, books are a perfect way to help inform and visualise the idea you have in your mind. "Cork, Bandon and South Coast Railway" by Ernie Shepherd would be a perfect resource for you with some station track plans in it if my memory serves me right, along with information on rolling stock and plenty of photos.
You are on the right track with the 'C' class. A filthy silver or green C class is perfect for the final years of the CBSCR. However there are not many other ready to run models of locomotives from the line available. 00-works are bringing out a 0-6-0 saddle tank at the end of this year that is based on a prototype from the CBSCR but it is rather expensive. Otherwise locomotives such as the Bandon tanks are only available as metal kits (studio scale models). I think 3D printed bodies of 0-6-0t No. 90 have been knocking about irish modelling facebook groups as well if that interests you.
The line had rather eclectic mixes of rolling stock that others on the forum could tell you about more precisely, but Bulleid corrugated-sided wagons were widely employed on the line, especially for things like seasonal sugar beet traffic. Kits of these are available from Provincial wagons.
As for making buildings, platicard will invariably become your new friend I would say. Find photos of the buildings you want to make and start trying to piece them together yourself. It is a fascinating line but will certainly require imagination and ingenuity on your own part to bring the model of it into reality, so enjoy the journey and experience creating it.