Brian, Like Bob, I use auto exposure (either center-weighted or matrix) and auto white balance. These new digital cameras have taken all the fun out of slide duping. Remember what a hassle it was with film -- filters for correct color temperature, increased contrast unless you used a special duplicating film, etc.? Well, all that's gone away now. Once you get the ES-1 and lens set up and focused, just start shooting. Problem slides may need some exposure or WB compensation, but you'll know immediately and can either re-shoot, or if you use RAW, adjust in PP.
Try it -- you'll like it.
John "One should photograph objects not only for what they are but for what else they are." -- Minor White