I've had good service from one of those super weed eaters on wheels, think it's a DR. At least, it would chop out everything but the 1"+ stuff. We used garage door cable in ours, and it just ate stuff up.

I've also used a pruning saw attachment on one of the interchangeable end weedeaters, with the shoulder strap it makes a pretty good bushwhacker. Useless in dead blackberry vines, though

Not responsible for advice not taken...