Mike, after watching one of Bob Rosendahl's live router demos 17 or 18 years ago, I went out the same day and bought a set of brass setup bars. They can't be beat for accurate standard size(1/8, 3/16, 1/4,3/8,1/2) setups or any combination of those sizes stacked! Most plywood dados I do are either 1/4" or 3/8" so makes it very easy to do as John suggested. I am still using that same set of setup bars today!
I have found that hand tools are the best choice when I want to make mistakes at a slower rate of speed.
I don't suffer from insanity. I enjoy every minute of it.