You can rotate joints while using the Paint Skin Weights Tool. This lets you test the way joints deform the bound geometry as you paint skin weights.

To rotate your joints while using the Paint Skin Weights Tool

1. Open the Paint Skin Weights Tool.
2. In the Influences list of the tool settings, select the name of the joint you want to rotate. For example, LeftForeArm (elbow).
   
3. In the scene view, -click to switch from the Paint Skin Weights Tool brush to the Rotation manipulator.
   
4. -click the rotation axis you want to rotate about, and -drag to rotate the joint about the selected axis.
   
5. Press the and arrow keys to select other joints up or down the joint hierarchy. For example, walking up the joint hierarchy to LeftArm (shoulder) or down the hierarchy to LeftForeArmRoll.
   
6. To switch back to the Paint Skin Weights Tool brush, click the currently selected joint.