Hello Jon. I could find no Blaney family in Longford in Griffiths Valuation circa 1854 or so but see a total of 17 Blaney people in the 1901 census, the main family appear to be Millers as that is the list occupation of a family in Creevy, Longford.
There is a heritage society in nearby Drumlish who recently published a book on the area, https://www.drumlishheritageandhistorysociety.ie/ not sure if it covers Clonguish but you can ask them.
There is also a Longford Genealogy Facebook page, not overly active but may turn up a lead. I am assuming we do not have a local volunteer there as the query is here over a week but maybe there is.
If you want links to the above they are here, http://www.census.nationalarchives.ie/ and here http://www.askaboutireland.ie/griffith-valuation/index.xml?action=nameSearch
There was recently a Who Do You Think You Are programme on an American Actor, she was from Clonguish, cannot remember her name but it is somewhere on that Facebook page, sticks in my mind as I correspond with a US lady from there. It was on PBS in America I think, about 2 months ago.
Regards
Pat