Scots and Irish in the Thirty Years War

What is the best source of information on this subject I wonder? Am I right in thinking Scots troops didn't use musket rests as in this picture? Longbows were involved? I notice there's an American group recreating Gaffney's Regiment. Also some stuff on Scotswars. A page on Mackays here.
Irish
Also there are a number of Irish officers involved in the death of Wallenstein and therefore in the Imperialist army. An Irish Captain Walter Devereux, a Walter Butler, and a fellow named Newman were present. Was there an Irish dragoon regiment in Wallenstein's army? Anyone have any ideas or information on this subject?