If you want to grow your following in your sleep (I know it sounds like a cheesey marketing pitch), here is what you have to do: find a few twitter stars- those with 10,000 plus followers that are in your target market- then late at night, say 11:00 or 12:00, right before you go to bed- tweet a good night message to each of these people. The message will likely stay on all night due to far less activity during these hours. Your @name will show up on their very popular blogs under their twitter feed for hours.
I tried this last night @posting to just three popular twitterers before I went to bed, and I awoke to over 30 new followers. Not exactly hundreds of followers, but it took me less than five minutes to send those posts. Imagine if I had sent tweets to all the top 20 twitter celebs? Try it out, and let me know how it goes for you.