Here's a decent on-road way to get from Brunswick to HF. The only slightly hairy part is the short section on 340 over to Keep Tryst Road. At first you'll swear you just got on the freeway, but it's not that bad. Bikes are allowed, and the shoulder is wide:

http://ridewithgps.com/routes/2877218

Unfortunately there's no left-turn onto the other end of Keep Tryst Road, so you have to ride a bit on 340. HOWEVER, if you're careful you can actually cross over the guard rails on 340 and catch Keep Tryst Road there. I've done that once. Now I just ride on 340 however.