Having said that, given how cheap 2mm models are, I've recently ordered a pack from Irregular Miniatures' Horse and Musket range. At that scale the effect will be pretty much the same as card counters. I'll let you know how it goes.
Anyway, to Friday. My brother came round to my new house and we christened it with a game of Give Them The Cold Steel, an excellent (and free) set of ACW rules. I tweaked them to change the scale, making 1" the frontage of a regiment so we could play on a map of six sheets of A4 paper, with the Trench Raiders plastic sheets to prevent slippage.
Using the Wikipedia page for First Bull Run/Manassas Junction, I created a 1" x 3/4" square for each regiment, and we picked the action round Henry House as the snapshot for our battle. That gave each player about five brigades (25 regiments) to handle. To the uninitiated, the rather awful film Gods and Generals does have some excellent battle scenes in it which capture the feel of the battle.