Victoria, I'm not sure I have much to add to help you out, but I would love to chat. We are in the process of implementing Sitecore, sounds like you have just finished.
One thing to keep in mind with Sitecore is that its ability to be modified for inline editing means you can taylor some of the experience to match what your users are used to doing. It can be an ever evolving process, change the interface to the learning curve is lessor. :-)
We are a small institution and are using a different CMS. I am responsible for providing training. I have taken the basic user manual provided by the CMS company and customized it for our institution. I have scheduled numerous in-person training sessions with varied degrees of success. Last fall I polled our CMS users and did not get any kind of consensus for preferences for time of day (I had offered classes early in the morning, after work hours, and during the day, and on various days of the week). Since it was difficult to procure a room that wasn't already being used for classroom teaching, I ended up scheduling a weekly one-hour class on Friday afternoons (when the room was available). Few people attended but those who did indicated that Friday afternoon was typically a slow time for them and perfect for training.
I am now moving away from providing in-person classes and one-on-one classes for individuals and will be providing online video tutorials instead. I think our less-tech-savvy users will miss being able to ask questions and having hand-holding. But the thought is that it will free up my time to do other things on the website.
I'm curious on the size of your user base? Do you have 1,000's of publishers, 100's? We've really been slimming down the number of publishers, and will likely increase the number of authors we allow into the system. But I don't think our number of authors is going to exceed 50' and number of publishers I'm hoping to keep around 10 or less. Which in my case makes 1-1 sessions hopefully manageable.
What I've done over the course of our institution's 5-year period using our current WCMS (OU Campus fm OmniUpdate) is to identify the tasks that end-users/content contributors need to do the most often, and then I used Camtasia to create a simple, under 15-minute, 5-step on-demand video tutorial that they can access whenever they want.
This has proven to be very helpful to our users, and has greatly reduced the amount of 'in-person' training session requests that I receive from the campus.
When I do receive a request, I first forward the URL to the 5-step training tutorial and then instruct the user to contact me if they have any further questions (for example, if they want to be able to do something that the video does not cover).
I have found that - by using this on-demand video training approach - I receive an in-person training request less than 1 out of 5 times a user contacts me to request access to edit their department's website.
To see the video set that I forward to my users (maybe it will give you some ideas..maybe not), go to: http://www.vvc.edu/videos/oucampus-5steps/
This video set covers the most-often used functions of non-technical campus content managers, which I have found to be:
And that's it...