I’m glad to hear there are other butterflies out there flitting around. Among my many ongoing – or, more truthfully, abandoned – projects is 10mm ACW. Here’s a few tips I gleaned from my reading at the time (it was quite cursory so I certainly wouldn’t dignify it with the name of research):
You need to use a bit of caution with the older uniform guides, since they tend to repeat the same mistakes. I used Philip Haythornthwaite’s ‘Uniforms of the Civil War’ (Blandford) and so the first unit I painted was the Irish Brigade, complete with green collars and cuffs, which it turns out they never had. The next one I went for was the Louisiana Tigers in their rather fetching brown jackets, which it turns out really should be blue.
The current thinking also seems to be that the whole ‘ragged rebs’ and Confederates in butternut thing has been a bit overdone in the past and that the supply system in the South my not have been as bad as it was once thought. I think supply was also the responsibility of the individual states so there could be variation within the army with regiments from some states being better equipped than others.
Finally your biggest challenge is finding the correct shade of blue for union uniform trousers. Sadly they are not the sky blue of the Britain’s toy soldiers I had as a child. Finding the correct colour is a bit like trying to find Polish crimson for Napoleonic lancers, whatever shade you opt for it will not be quite right.