I have seen a couple services ( ManageWP, BlogVault ) where we supply them with the admin login details to our WordPress site and they programmatically install their respective plugin and then connect to it. I am working on a project where I have to migrate a few hundred WordPress sites, doing them individually will be a time consuming task so I am trying to automate it.

I have looked into XMLRPC and cURL but have hit a wall. For e.g I can script the login form using cURL, but then don't know a way forward to install the plugin. With XMLRPC the wp.UploadFile method only allows jpeg, png and gif files to be uploaded. Will appreciate if someone can point me the correct direction.