Common privet, Ligustrum vulgare, responds extremely well to even quite severe renovation, as do most other privet types. These plants will regrow from hard prunig down to just a few inches above ground. That may well be much more than you need to do but just illustrates what can be done.

Now is not the time to do this. Late winter after the worst of the cold weather is past is ideal for a major pruning but you can do some tidying before that if the situation is intolerable. First, make a determined effort to rid the area/hedge from any weeds or under growth. I'd mulch after weeding/cleaning out both to keep additional weed growth to a minimum but also to conserve soil moisture and provide a little nutrient boost. Keep mulch away from direct contact with any wood stems. In mid/late fall you can groom the hedge, removing any overhanging or fountaining bits. These are very likely shading out lower growth and causing it to look woody and sparse. Ideally, hedges should be pruned in an 'A' shape - wider at the base and tapering up to a narrow top. This allows sunlight to reach all surfaces and should result in much more even foliar growth.

In March or so, you can do a harder prune if you like to reduce size overall and to clean things up. Removal of any dead wood and some interior thinning should help to encourage new growth.

Gardengal, I have to compliment you on your helpful replies. I always enjoy reading and learning.

gardengal,
thanks very much for that reply. I will do a major ground cleaning this fall, and maybe remove some obvious death (there is quite a lot of large dead areas). I do also have a large overhang all along the 150 or so feet. Another major problem is two different types of weedy vinery that if not constantly removed will grow over an entire area and seems to suffocate it. In the fall I will also go into this hedge and cut down these at the base and soak the exposed area with vine killer like a poison ivy liquid.

I cut down about 30 feet of over 18 foot privets two years ago; I'm glad that I did it, and the hedge looks great now, but jeez louise it was a hellacious job.

The privets just shrugged off my electric chain saw, and I ended up doing the whole thing with a hand pruning saw. The wood is dense and quite heavy, and the interior branches are unyielding. And then you have 18 foot long poles to deal with. If I had to do it again, I would pay a tree company to do it - they come in with the heavy-duty chain saws and the chipper, and can be done with it, leaving you a nice pile of wood chips, in an afternoon.

If you have a heavy-duty chain saw already, you're in much better shape than I was, but getting rid what's left once you cut it down is daunting.
Please believe that I am not saying you are incapable of doing this, or that it's Herculean, but it is a long, long job without lots of power equipment.

FWIW, I cut them down in November - I couldn't stand looking at them one more day - and they were fine.

lisanti07028................I dint expect for one second that this will be quick or easy. It is 150 feet of 7 foot deep jungle! Lots of dead, 2 and 3" diameter stalks. I plan to rent a pole chain saw and spend most of the day outside. probably pull my sons pickup right to the back of the yard and pile the cuttings in and make several trips to the dump. Then rake everything out from underneath! I plan to lose 10 pounds that day, but I need these things to recover and green up and look presentable as they are a fantastic natural fence. Thanks!