God can add grace to works and law keeping but He can't possibly add works to grace. If you add works to grace, then it is no longer grace, but wages earned.
How does God add grace to works?
At what point does he do it?
How much of the law must be fulfilled before God adds grace?
Jesus fulfilled the law for those who believe in him. Though Jesus crucifiction and resurrection we are circumcised - perpetually, both Jew and gentile, because "circumcision is circumcision of the heart". We have also entered into the true Sabbath rest just as we also have had every "jot and tittle" of the law fulfilled for us.