I don't think the pliers will grip the spokes well enough to stop the twist. The "flags" you plan to use will be all you need to manage the twist. Use the technique of overshooting your desired nipple position then backing off (either when tightening or loosening) to avoid the spoke twist as much as possible. Hold the wheel vertically and compress the rim against the floor (thin carpet or bath mat to protect the rim and floor) using your body weight in six separate positions around the half-circle to unload the spokes and allow them to unwind. You don't have to go all the way around the circle this way, because each position fixes both top and bottom, i.e. both sides of the hub. Do that several times as you bring up spoke tension and one final time. As long as your flags are in their neutral position, it means you are good to go.