Originally Posted by Drew Eckhardt

You don't need to hold spokes.

Put a tape flag on the first spoke after the valve hole as close as you can to the nipple without interfering with your spoke wrench, and another on the next spoke when you're dealing with dished (most rear and disc front hubs) or mark the spokes with a sharpie dot.

Watch how much windup you're getting (assuming no sticky nipples all the spokes will be about the same in that wheel half, or both wheel halves for symmetrical wheels). Overshoot by that much and backup.

With reasonable spoke counts (32 +/- a few) you don't need to be more precise than quarter turns. Add 1/4, 1/2, or however many turns you want, plus the extra for windup, and back up so the spoke wrench is in the appropriate position parallel or perpendicular to the brake tracks.

Anti-seize (my favorite, will prevent galvanic corrosion), grease, or oil on the spoke threads will limit windup. The same in the nipple sockets will limit how hard nipples are to turn.

To undo any windup you can also put a block of wood on the ground, stand the wheel's axle on it, and push 180 degrees apart with your hands moving around the wheel thus unloading the spokes enough to turn back; although you're better off just avoiding it.