There are different opinions. Mine has worked great for me for nearly 40 years.
The sling does the work of holding the rifle. The stock is forced into the shoulder pocket. The forearm of the rifle rest in the left palm (I'm right handed). The left hand does not grip the rifle. I do not have a firm grip with my shooting or right hand on the pistol grip. With a firm grip its hard to move the trigger finger without disturbing the rifle. I can drop my right hand without disturbing my sight picture.
I shoot this way better then I can if I shoot of sandbags or any other rest, but you can use a rest also by laying your forearm of your slung arm on the rest.
I know you said you plan on shooting from the bench, you can do this slung up, or setting or kneeling. It works while hunting leaning over a rock, against a tree, or resting your left forearm on you pack. Also worked well in LE while leaning over the hood of a patrol car.
The ideal is not to use any muscles to hold the rifle. The sling and pocket of your should hold the rifle, your head is rested on the stock giving you a chipmunk appearance. Again only enough grip with your shooting hand to keep your hand from falling off the pistol grip.
Again this is my method, my opinion, I'm sure the bipod guys with rear bags are different.