Remember as well that you have a floor behind you and that the direction of gravity has changed!!
I know a lot of wing chunners make the mistake of trying to grapple using wing chun! Rather than learn a grappling art.
But you are right with using legs sometimes and arms other times
WC punches aren't gravity based and already being trained in very close quarter attacks helps when someone wants to give you a hug. I recommend anti-grappling over grappling.