You're in for some fun, I hope! The good news is that bowgun controls are really simple, but the bad news is that a level 140 Shagaru won't give much margin for error. I'd recommend practicing on "Heaven's Wheel", "Stop the Wheel" and "Wheel of Time" until you've gotten the hang of it.
Alternatively,
here's an 11 minute run with the Seregios LBG instead. This hunter gets knocked around more often, but he's using a Heal-honed weapon to keep going without having to sheathe or heal. It's a novel approach that might be more friendly to newcomers.