Back when I only used walk-behinds, my hands ached to the bone. Getting a rider is what kept me in this business. But your problem is more severe than anything I experienced. I was speaking with one of my competitors this past fall and noticed his hands. He can't straighten them. He's not sure how much longer he can do this sort of work. There's a fellow at the local Lesco whose got a hand that flops around like he's got parkinsons. But it's the result of nerve damage from using weedwackers all day! I recommend that everybody wear leather gloves when they operate a walk-behind or wacker. It helps. If you are using a weedwacker that is vibrating noticeably, throw it out and get a new one. It's no time to be cheap. I recommend the Kawasaki KB-26A. Lightweight. Good power. Very durable. Lesco sells them. To continue to use a wacker that vibrates is foolish since now you know nerve damage can result. To all the guys with hand pain, I'm real sorry to hear about it. That's a serious problem.