"pantoute" means "not at all", so "y mouillera pus pantoute" literally means "It won't rain no more at all".
"Y n'en portent pus pantoute" means "they don't wear them at all" so I'd say that it either means "they don't wear little short dresses any more" or "they don't wear dresses at all" (they wear pants)
I don't think you missed any Québécois slang Jim. You wouldn't sing the 1st verse in France French as "branler" is dated and seldom used to mean "to wobble" or "to nod".It's mostly used as a reflexive verb to mean "to wank" (lit.) or as slang for "to do" (Qu'est-ce que tu branles? = What the fuck are you doing?)