Fr0zen- Another good reason to clay before polishing is so the contaminants aren't smoothed by the polish (which would make it tougher for the clay to "grab" them). I'd order the Block and Glide clay package from the Autopia store. My initial impression is that it's better than my previous clay (Griot's). If you wanna go local, try to find the Mother's clay kit or Clay Magic. Check auto stores.
And yes, the white pad works well with AIO.