They really arent that hard to tell apart. Canadas have a black head, white fronted geese are grayish brown. White fronted geese also have a distinctive white band at the base of the bill. Specklebelly's also have orangish feet, canadas have black feet.

Shouldn't be too much confusion. They really don't look all that similar... not too sure how they look in flight; I've never hunted them before.