Go to the page of your number one artist (or of the week) and follow the link of its number one similar artist. Repeat that for this artist and so on, noting each artist as you go. Do this until you've got 50 artists (not including your number one). If you get any repeats, just go to the second similar artist or the nearest one that you haven't already listed.
This was kind of stupid and pointless, because all of the bands end up being similar and there are so many repeats. By the time I got to some artists, I had already used all of their top 10 similar artists. So it's kind of stupid, but I was bored.