And since YD is advised to "Mind the music and the step," I assume we're also supposed to think he's a foppish and effeminate fun-lover.

It could well be that "with the girls be handy" imply "cleverly ingratiate yourself with the girls," as at a ball. Just a guess.

Otherwise, I agree that "handy," at least in America, is an everyday term meaning skillful (at something) or (also) readily available.

But it no longer means "clever," which may account for some of the uncertainty.