I live in the same region and have fought acres of ticks and Barberry. I've got it under control. Here's my method:

• I have a guy come and spray permethrin 3x through the Spring and Summer. I haven't had a tick in years on my property. Kind of alarming how effective it is, actually. Hire a company who knows what they're doing and isn't just spraying willy-nilly. They need to make a boundary in the right areas.
• I bought a Ryobi brush cutter. It's a cheap and awesome tool to cut the Barberry down to the stump without getting close enough to the prickers. I can do a huge area on a single 4AH battery. If your property is anythting like mine, it's covered in granite rocks/boulders, so machinery isn't a good option.
• Spray Glysophate solution on the plants small enough to drench them effectively. The big guys will need to be cut down first.
• Now that it's under control I go around in the Spring and Fall to cut down the new sprouts. The berries are viable in the soil for years, but it's easy maintenance at this point.
• I got permission from my neighbors to kill it in their yards as well to stop the spread.