Animating a mask in a circular path

Hey there. this is more a animation based question.

I know that you cannot use motion guides on mask so i was wondering how i can create a animation to reveal a pen style highlight… like when you circle a piece of paper to indicate something of importance.

what i have tried is the obviously frame by frame animation of cutting out the shape to reveal a section of it each new frame, but thats just time consuming and well you dont have speed control (easing as well).

I have tried using a graphic in a graphic animated by a motion guide and using that graphic as a mask and that sorta works but it dosent really help since you need to make that motion guide graphic reveal as well, so its actually double the work.

just wondering if any one has some method that would be helpful.

:oh i tried shape tweens and while im pretty good at them, they seem more trouble than help with a circular motion. shape hints helps but it again is too much work for such a simple graphic element.