i have ridden this (actually a good deal beyond kittanning) 3 times in the last 2 months... it's a pretty easy ride, and i've tried it a few ways, the best way from my experience so far is cross the river at highland park and get on freeport rd, take it all the way to trenetum. after trenetum start to hug the river (but don't go under the rail tressle into the park) on 1st ave/river ave and just follow it around (the is the best part of the ride, little traffic, decent road, riding through little towns and a cool scrap yard and some big industrial complexes), eventually you'll come to a switchback that is brutal and short at the dead end of the road, you'll climb up that and it will take you to a crazy downhill into freeport, cruise through freeport and then a little ways out of town you'll hit 128 into ford city, this road is great, through farm country, rolling hills, i handled it ok fully loaded on a single speed but you could really cruise through here on a geared bike, there are no tricky turns or anything, just keep going, eventually you'll hit the bridge, cross the river and immediately on the other side there is a rail-trail that you can follow all the way to kittanning.
this is a great ride! have fun, feel free to ask me any questions if you have them.
the only alternate route that i haven't tried is crossing the river @ new kin and taking leechburg rd to leechburgh... if this is relatively flat it would be the best way, you can pick up a rail trail shortly after you hit leechburg that will take you all the way to kittanning... if you want to take one for the team and try that out for me i'd appreciate it 
