Twitter followers are almost same thing as people in your mailing list. They will see your every update.

You can make many micro mails like "Checkout this cool free video that I've found. It explains how to get 100 visitors a day with 5 minutes of work! [LINK]" or something like that. However do not spam your twitter followers like most of the marketers do nowadays. If you tweet them too much they will automatically pass through your tweet.

More followers you have - more people will see your tweets, just like an email list