Years ago, I bought a deal for a dollar at a farm sale, that worked very well for unrolling four spools of barbed wire. It was made from 2" x 12" lumber, and contained five boards about four feet long. Each board was standing on end, just the same distance apart as a spool of wire. The boards were their own runners, and the contraption was pulled on the ground. About ten inches in from the backside of the lumber, a hole about an inch and a half in diameter was drilled through all five parallel boards. A one-inch pipe went through all the boards, with pins on each side to keep the pipe from falling out. This allowed four spools of barbed wire to all be unrolled at the same time, as the sled-like contraption was dragged along on the ground. Bracing made from boards across the top kept the affair held together. Outside of being a bit cumbersome to haul around, the outfit worked like a charm.