I gather you want to burn it, burn it all.....
You might be as well getting a man in with a digger for a week or 2 as, together with tearing out bushes, he'd be able to patch holes in the ground, build up ditches, make gaps etc. You'll probably still have to burn a few piles but its safer than burning open ground. Weather has been so wet lately that probably hard to burn it on the ground but risk of spread not that high either.
Also, if you have any cattle, or maybe there are neighbours with cattle, you'd be surprised how much they clean it up/open it up, assuming theres at least some grass on it.