Try walking with a crop and tapping/bumping him in the shoulder and flank area when walking. Just walk, walk, walk, straight, zigzags, circles, etc. When he misbehaves, bump him with the crop. If he doesn't listen, bump harder, turn him, make him pay attention to you.
I used this method on my gelding who would fidget like mad when standing tied. I would just tap him on the flank when he started getting impatient.