I understand goats love blackberry vine salad. Honeysuckle too if you have that.
This :number1:
Forgo the spraying. You (and your ground) does not need spraying.
Rent a small walk behind mower and mow it down first, but be warned that it is a friggen workout! Tractors with a rotary mower are much better. If you can, post a help wanted ad on Craigslist for tractor work. Someone in your area probably has a tractor with a mower that is more then willing to help out, for a small fee.
Once the brush is mulch, pulse a goat or three though in a paddock shift system (set up 2 or 3 pins, and move them around the area when the area is getting low). These dont need to be YOUR goats. Again, see if anyone in your area has a few goats they'd be willing to bring over for some free food. Goats are really good at eating just about anything. If you wish to own your own, they are great for small homesteads, but do your research first. Goat milk is awesome!
Alternatively, and what I would do with my tractor, is mow it down, then use teeth on the bucket of my FEL to remove the roots the best I can. Take it all the way down to bare earth if possible. Even go as far as rototilling the area. I would use my BH to remove any stumps as well. Stumps are always in the way. I would then seed back with a pasture grass mix of dutch white clover, vetch, fescue and the like. The thought process here is to get a healthy layer of seeds down quick. Nature will fill the vacuum with things like weeds if you don't fill it with beneficial plants first. Once the plants have matured, I would then pulse whatever animal I want though the area on a paddock shift system. You'd be surprised what goat or cow can do to the land, in terms of making it better, if properly managed.
Hope this helps. And good luck.