How to get rid of huckleberry on the forest floor to allow regeneration?

in the late 90's my farm was logged pretty heavily. Since then only about half has had natural rengeneration of trees, mostly black birch with some oak. The Western half is overcome by huckle berry or low bush blueberry which blocks out all sunlight to the ground. Mowing isn't an option due to the rough and rocky terrain. We have used herbicides to control some but it seems to be very persistant and with the dense roots and leave blanket it is hard to get to the soil to plant native species. Any other advice on this would be great.

Have you talked with a consulting forester?  They could visit the site and assess the situation directly.  It's likely something they've dealt with in the past.