Instead of "measure twice, cut once", my technique was "measure and adjust for 30 minutes, cut for 10 seconds" because I am very detail oriented.
This changed when I watched a woodworker from "the old country".
I wish I could share the actual experience with you, but I once went to a WW demonstration where they brought a guy in from Sweden to make a stool in 2.5 hours using no power tools.
Working fast using only had tools was very interesting, but the thing that really stuck with me was that he not once read a measurement off of a scale! He did have comparative or transfer devices, such as a simple divider or bevel such as:
http://www.woodworkingshop.com/cgi-bin/549F2F57/mac/additmdtl.mac/showItemDetail?loadItem=CN00117. He sighted down this alongside the bit and brace when boring the holes for the stool legs so they would all have the same angle.
I don't know why, but this was a major epiphany in my life. Even though I am an engineer by training, I almost never use measurements any more.
If I am setting up a dado on the router (using two passes as you suggest), I use a scrap of the actual plywood as my gauge. Why transfer to a number and back? It takes time and is a source of error (2X the resolution of the measurement device).
For the quasi-DIY subs I am building, I picked up one of these:
http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=96509
I will use it to transfer the dimension for the diameter of the speaker and adjust my router circle jig to match the calipers, there is no need to ever read the dimension.
Historically, there was little need for measurement devices in manufactring until industrialization mandated that components fabricated at one location fit components from another location.
Next project, give this a little thought as you are transferring measurements. I'm betting you will find your fits are just that little bit better and much quicker as I have.