Handling Multiple Authors On Many Blogs

I tried this one here and got no response so I will try it one more time worded a bit different.

I have about 20 different wordpress blog on different hosts all separate install and all have their own DB. Currently there are about 15 authors but I expect it to grow to somewhere around 100. Also my number blogs will grow to about 30 to 50 depending on success.

My problem is that when I want to add a new author to all the blogs it is very time consuming. I have to assign passwords and username 20 separate times one by one.

Can anyone recommend a method to automate this? How should I approach it or have a programmer approach it?

I would like to enter an author 1 time and have it populate the correct tables across all my blogs with the same user name and password.

Your suggestions are greatly appreciated. If there is already a plugin that does this I would appreciate that as well as I have been unsuccessful in finding one.

Thank you.