Better way to update a user's group role

My example:

I have a group type called "Stores"
I have created about eight stores.
I have created an global role called "Management".

I have assigned members to each store (by going to add member per group entity) and adding the role "Management".

However if I want to change the role for a user for all the store entities I have to open each group entity seperately, go to the members section, edit user and change role. Even with eight group entities it takes a considerable amount of time.

Is there anyone that knows a solution to this? I have not experimented with rules yet, but I am guessing that is the only way to go. Just for reference I am not a coder.

Thanks