I think these questions pertain to all brewers, not just extract brewers. My sanitation process is just about the exact same as an all grain brewer as it was when I was doing extract. I don't see anything wrong with your process, especially if its working for you.
I mix up Star San in a bucket and usually only mix up 2.5 gallons just after the boil has started. As mentioned above, I then pour about a gallon in a carboy, shake it up and lay it on its side. Every 10 minutes or so, I'll rotate the carboy to ensure the entire inside surface gets a few minutes of contact w/ Star San. When I'm ready for the carboy, I pour the sanitizer back into the bucket through my strainer to sanitize the strainer.
Also, get a spray bottle and put some sanitizing solution in there. This can come in very handy for many uses.
I can't remember who it was on this board, but I went to Home Depot and picked up a dry wall mud tray. This tray is perfect to keep utensils in sanitizer while you work.