user management

I am looking for a way to add a user and delete a user from 20-30 sites easily. I couldn't find a plugin that did so explicitly.
We have contractors come on board that need access to several sites. When they leave it's always a mess going through our 87 sites to see which ones they need to be deleted from. Often the documentation is not there to guide us.
Do you have a plugin for this? I think infinitewp does ( but I want to use wpmu if possible. Do we have a way to so this with our plugins?