One of the best method will be Social Bookmarking. Hire someone for doing submission to top social bookmarking websites and enjoy your increasing visitors.
Im not saying its easy but, i have sold over 20 social bookmarking websites, and 10 wordpress sites on flippa, and all of them, was ranked 90k in alexa and was getting around 1000-2000 visitors a day, all you have to do is build back links, and not blog commenting, i mean real high quality back links that someone will actually click, like forum posting,stubble upon, and social bookmarking.