Bulldogs have all sorts of idiosyncrasies, and packed awful glands are among them. The vet did it himself with no fuss for him or the dog. Just slung an arm over his butt and went to work. He used a cotton ball and expressed the glands. The dog hadn't exhibited any problems but at least I knew what to look for after that introduction.
My suggestion is: Just go easy the first time with no trauma for either of you. If one is clogged, the attempt will stir things up some and the next time or two it will get easier to empty, and both you and Mason will be more at ease (if there is such a thing) with the procedure. It's better to do them regularly, or whenever you see him scooting. licking his bum or reeking.