I'm in the process of tearing the wallboard off of the interior walls of my attached garage in order to insulate them.

I'm using kraft faced rolled fiberglass and stapling them into the cavities as properly as I figure I can.  In spots where it seems appropriate I've tuck taped seems or edges.  I haven't taped the tops or bottoms of the cavities as my understanding is that the kraft backing is sufficient enough of a vapor barrier.

As I finished the first wall and rounded a corner, I realized that I could see daylight coming from between the wall studs and the exterior wall panel.  Just a thin sliver at the bottom.  That made me realize that maybe I should be caulking/foaming these cavities before the rolls get tacked in.

My question is, is this practical / necessary?  I understand that air flow kills the effectiveness of insulation, but will the paper barrier and / or a combination of tuck taping on the interior side stop air from moving around?

What would a pro do in this setting?

I would use spray foam and block it from the outside with wood or whatever is used on the exterior. Mainly due to critters

I'm not a insulation pro but any opening from inside to outside is a no no for me unless it's a door or window

Huh?

at minimum you need to spray foam or caulk the gaps.

An air barrier is just as important as a thermal barrier.

You can buy the pro guns and foam canisters at home depot that costs much less per ounce than the toss away cans and is much easier to use.

The Great Stuff Pro cans are definitely not cheaper at my Home Depot. They're cheaper if you plan to use some and store the can for later, maybe. If it's a one-time use, the Pro cans are actually 2.6 times as much per oz. and then you need a $0.74 tip for each re-use.

Great Stuff 16 oz. - $3.78
Great Stuff Pro 24oz. - $14.97
Great Stuff Pro Gun - $48.92
Great Stuff Pro Gun Tips - $7.37
Great Stuff Gun Cleaner 12oz. - $7.47

I really can't see the point of the Great Stuff Pro. It makes no sense, even for pros. By the time you spend $63.76 on a gun, gun cleaner, and tips, you could've bought 16.8 cans of Great Stuff. Then all the time you waste cleaning the gun when you're done. And that doesn't even factor in that the Pro cans are more expensive per oz. I have no idea how you're supposed to save money with Great Stuff Pro...

You can also use chlorinated brake cleaner to flush out the straw of the standard cans and use them at a later time.