A good rest IMO is a requirement. I hunt on the ground 100% of the time and finding a suitable rest can be problematic, a bipod or shooting sticks instant solution.

I can understand his viewpoint being I too was taught and learned to shoot off hand. It was how it was done before these aides were common, older dogs take time to learn new tricks. Have him shoot off yours, he may just change his opinion slightly. I know I rarily shoot off hand anymore, it just gives more more confidence to have a solid hold.