An expert of older times whose skills have regressed is:
- out of practice;
- formerly skilled;
- in need of training;
- erstwhile expert;
- veteran beginner;
- false beginner;
- remedial learner.
His skill in question is antiquated. I'm looking for a better adjective to state that a skill needs to be refreshed.
For example: I'm out of practice of cooking. (I apologize for the poor sentence. It is the problem exactly).
I've already seen this similar question that does not have an answer.