David,
I live in Bennington, VT and spend lots of time in Brattleboro riding the area. We are heading there now actually.
Here is a little rundown of the route to Granville you are looking at. All of it is quite beautiful and I'm sure you will enjoy it.
Brattleboro to Newfane is flat with a wide shoulder.
Newfane to Jamaica is fairly flat with a decent shoulder. Light traffic.
Jamaica to Bromley is a long steady climb with short steep sections. The shoulder here is not generous but there is light traffic.
Bromley to Manchester is all downhill but the traffic is more steady. The shoulder is okay but is more narrow as you get closer to Manchester. BEWARE the outlet stores in Manchester = lots of traffic!
Manchester to Granville is fairly (mostly) flat with ice views of the surrounding mountains. The shoulder is pretty good until you hit the small towns. Traffic is generally light.
At the jct of Rtes 30 & 149 bear left onto 149 for a few easy miles into Granville.
Enjoy your trip!