How likely will an Army Reserve unit with a vacancy process a Gray Area Retiree to fill that position? What is the process?

It's a long process SGM but it can be done so long as you are not collecting a retirement check yet. I can help you as well.

I can send you the info and process. Email me [login to see] . It's up to HRC if they will transfer you back in.

I suggest you work with only one Army Reserve Career Counselor. It's not added value to have multiple counselors working your packet because only one of them will receive credit for your transfer. Do not be fooled that one can work your packet faster than the other.