The Sharpmaker is really not suited for reprofiling knife edges, especially on a knife as large as the RAT-7. Not sure what to tell you about getting the edge in shape. There is literally a TON of info on this site about sharpening. You might want to do some exploring.
Sharpening is hard work, especially if you are reprofiling the edge. But a good edge is worth the work. If you are trying to remove significant metal, you need more than the Sharpmaker. Sandpaper, stones or diamond sharpeners will help shape the edge a lot more quickly than ceramic stones.
. . . deliverance will not come from the rushing, noisy centres of civilization. It will come from the lonely places. - Fridtjof Nansen