I use a piece of H beam a little wider than the axle, chain the axle down around the spring, and jack up under the spindle area with a big bottle jack. A steel block supports the axle just inboard of the spring, so the bending force is applied under the spindle. That is to move the camber in the negative direction. To make the camber more positive, chain the axle to the H beam at the spindle area and inboard of the spring, and jack up on the spring seat. It's all simple geometry. It's usually necessary to move the axle a little beyond the desired correction to allow for spring-back when the load is removed. Yes, on a pickup sized axle, it's all done on the vehicle.
Jerry
