Webb's performance over Kerry could also be accounted for by the overall national Dem trend in 2006 that independent of any candidate/campaign effort. Difficult to measure in a state like VA because there were no other competitive federal elections in 2006 to serve as a reference point. They hold state elections in odd-numbered years and the CDs are so gerrymandered that they've barely seen any party switching since Virgil Goode voluntarily switched over to the GOP.
Perhaps comparing Webb's performance to that of Tim Kaine's governor's race in 2005? Kaine was certainly not a good ol boy and his performance could be used as a better reference point than Kerry as to Webb's abilities to bring in what one Virginia political consultant calls the "Bubba" vote.
The map below compares Webb's performance to Tim Kaine's. Bluer areas show where Webb ran strongest compared to Kaine. As you can see, he ran well in northern VA and in the Appalachian areas in the southwestern part of the state.