Welcome Finbarr:tumbsup:, used to walk the line quite a lot back in the early 00's when i lived in the area.
Theres a few books you should get to help you on our way;
The Irish Narrow Gauge, A Pictorial History, Volume One, has a full chapter on the Blackrock line plus has pictures of the locos after they moved onto the other narrow guage lines after the blackrock line closed.
The Cork, Blackrock & Passage Railway by Colm Creedon was available in Cork City library up to a few years ago, i doubt you ll pick up a copy anywhere else,
The Cork, Blackrock & Passage Railway by Stanley C. Jenkins(oakwood press) would be another good one to get.
Best of luck with your adventure