Ross Beattie of Sydney, Australia has researched the McBrien families of County Fermanagh and also provided history on the Parish of Inishmacsaint.. Many McBrien's married Dundas ancestors also. His website is below. Click on the address, then click on McBrien and explore the Inishmacsaint and Lower Lough Erne links.
More specific information on my McBrien branch can be found at: