They're interface is a nightmare. If you're doing this for an auto draft, I think the easiest thing is use "Do Not Draft". It sounds insane, but it works. Just go through the top 100 or whatever, and anyone ranked too high in your opinion just move him to do not draft. When you're done, you'll have a top 100 pretty close to what you want. You may want to go into positional rankings as well, esp in larger leagues.
If you plan to be at the draft, don't do this. It messes with the player pool.