Working in stages just means that you sharpen the edge a little at a time. The more pronounced the curvature, the smaller the bits you work with. For example on this blade :
http://www.physics.mun.ca/~sstamp/images/blackwood_hawk.jpg
I took it in I think three parts. The first part was the flat bit near the start. The second the part inbetween it and the start of the hook, and the last part was the hook itself.
Just take the edge and see it as a few straight lines instead of a curved profile. Then take each bit in turn and sharpen it. Turn the knife until the part you are working on it straight across the hones. You then work on this part until sharp. Then move to the next bit.
If you have access to power equipment then you can sharpen curvatures even like the above easily. I have found it much easier to get a smooth edge with a belt sander than trying to do honing by hand - which seems odd.
Another method is to use sandpaper on a soft backing. I have tried this and it will sharpen even odd curvatues easily. The edge will sink into the backing (I use thick leather or foam insulation), to the correct amount and thus you automatically match the angles without really trying.
The last time I sharpened the Machax from Camillus I did this and it has a more pronounced curvature than the above Hawkbill (from Neil Blackwood).
-Cliff