Mentorship is about raising you from the level you are at to the level you want to be !
The mentor you want to follow must posses some skills for eg he should be good in Physics, Chemistry and Mathematics and if a mentor is good in mathematics only he will be good mathematics mentor.
Mentor must be able to improve you and he must understands you what problems you are facing and he must be able to raise you to the level you want to be.
How could you know that the mentor can make you skilled ?
This could only be checked by following his content and advice and to test them in your your journey, You will feel the change within you and you would be knowing whether you want to seek guidance from him or not.
It is good to have a mentor whom you admire , you recognize his qualities and you want to be like him in some aspects.
Mentor should not be judged by his AIR but by his capabilities to improve you.