Seems to me that seeking out the 4lane state routes, complete with town bypasses, is a cheat, getting the ease of travel of an Interstate without the traffic. I thought the whole point to taking local roads was to slow down for towns every 10 miles, and lolly gag behind a farmer tractor for a mile or two. Plus the fun of passing slow traffic on the two lane highway! Don't you miss the buffeting as a semi passes by coming the other way? And the glare of headlights at night?
But if you really want to go local, it's hard to beat bike packing. Years ago, in preparation for a Mpls to Chicago bike ride, I ordered a full set of Wisconsin county highway maps. With the exception of the granddaddy of all rail-to-trail routes, Elroy Sparta, I rode the lettered ('A', 'P', etc) county roads where possible. Only took me 6 days, and I still remember the route better than any car drive 40 years ago.