We've tried 2 things each with their own pros and cons, so it's at least something to think about if you're starting your own troupe or you're noticing some issues with the way you're currently solving the problem.
The first solution was to hit the stuff that "newbies" need, yes-and, don't deny, starting scenes, vapapo (jill bernard), how to play a game, how to express a relationship, bring a brick, etc. Seems like a good idea, and you've got all those oldies to help you teach it, right? Well here's the problem: everyone else already knows this and knows it well. And for us it really wasn't doing that much for our new people because they were playing with people who were plateauing. Once all the oldies were bored it messed up all kinds of stuff. Newbies weren't learning, nor were they becoming part of the group because the elephant in the room was that the newbies were the reason we were doing these "newbie workshops." (This solution could still work if you made sure to vary it up and not do EVERY practice geared toward new members).
The second solution was to just carry on as usual, outside a few sessions of breaking-it-down for the newbs, and just teach the workshops that were relevant and that the whole troupe needed work on. It was amazing how much faster the new members learned when they weren't focused on the lesson, but on the fun. And everyone pretty quickly got used to new people being in the practices, which helped because the newbies had people to ask questions if they had any. The downside of this was of course the steep learning curve for the new members, but I don't think any of them would say they haven't caught on.