With the light's goodman on your left, take your right hand and place it on top of the light. Grab the light body with your right hand and slide the goodman off your left.
Dump/add etc
This "top hold" with the right is a temporary hold. Works perfectly and no wild light signals, continue to look at stuff, etc
You'll also use this same "top hold" when you check your SPG. Switch the light to the right hand and keep it pointing forward for good passive communication. If it's dark such as a night dive or in a cave you can illuminate the SPG for a second and get the light back up where your team can see it and know that your OK. Now your SPG is glowing and can be read with only the left hand and the rest of the team doesn't have to look to see what you're doing.
You'll also use the "top hold" when your moving your light cord around your long hose during an OOG.