Brambles are goats favourite food - depends what you want to do with the land though.
Do you want to make it look like a lawn? Or do you actually plan to keep goats or sheep or other livestock in long term?
If you just want to relatively quickly clear the land you would need a loooooot of goats and later flail all of the land anyway.
Brambles will keep growing back for at least several years of continuous browsing.
Personally I would clear some of it, and regularly mow the footpaths etc and let goats slowly eat into the rest.