Well, speaking of second attmepts, this is mine.
Last summer I attempted a ride from IN to DC via the Great Allegheny Passage. The original plan was to use some of the OH bikeways you refer to, as well as a small segment of the Northern Tier route. I found the backroads in IN and OH to be great for biking and decided to just improvise my route from western IN to Wheeling WV. I did use some bike paths and the Great Allegehny Passage (GAP).
Here is my two cents:
1) Off road bike paths in the flat midwast are more trouble than they are worth. One near Newark OH was so slippery I crashed. Most of the back roads are flat to gently rolling and far more interesting.
The main bike routes in OH F, CT may be good but so are the hundreds of other backroads to choose from. I have read that parts of the CT route are chip sealed which can be a drag to ride on. The people I encountered across OH were not accustomed to seeing touring bicyclists and were very helpful with directions and encouragement.
PADOT has laid out a grid of mostly on-road bike routes. I used the "S" route to go from Wheeling to West Newton where it merges with the GAP. You could use the GAP to go west around Pittsburgh and hook up with the CT trail.
The GAP isn't quite finished yet, but it is an incredibly nice ride. And the towns along the trail are dying for your business. The section of the GAP through Ohiopyle State Park is really wonderful.
The C&O towpath can be a quagmire so plan accordingly.
Check out
www.indc2003.crazyguyonabike.com for a blow by blow account.