I think I used a shapton 500 but save some work and get a lower grit stone. I like the Nubatama 150 a lot for thinning and that's what I use at the shop:http://www.chefknivestogo.com/nuba150grwa.html
Usually I will just find the edge (you can hear and feel it with a little practice) and then drop the spine down just a little bit to thin. If you do this you can grind until you form a new edge or you can remove some of the steel behind the edge and then lift it up again and resharpen the edge where it was before. The Edge Pro guys are much more into using precise angles when they do this but since I free hand I just do it by feel.