Hi everyone, only just found this post after having the same issue, however managed to find a very useful tool made by David Torno via Lesterbanks website, which may save hours of painstaking searching and/or animating.
https://www.provideocoalition.com/mask-adjuster-free-after-effects-script/
Its an ingenious solution to a problem that shouldn’t exist in the first place.
Hope it helps.
D