Information on the Route 4 / Woodstock detours...
For tourists (pdf)
For truckers (pdf)
If you're coming up I-91, Dugan's directions are optimal ... 103 to Ludlow, then 100 north to 4, then west (and a plug for Bagel Basement in Ludlow where 100s meets 103).
Coming from 89 in NH or have a target on the north side of Rte 4? Go up 89 to exit 3, then follow the detour which is rte 107 west to 100, then either south on 100 to 4 (Killington) or north on 100 for Ellen & Abraham.
Tut ... I don't have my map tools with me, but 89 to 100 to 4 might be better for you than 7 to 4. The latter has a lot of slow villages and is quite the slow strip up by Burlington. 100 is also a much more beautiful drive.