Timy,
A convex can be done by slack belt, Flat platen or the Tank track convex grinding attachment.
On the KMG attachment you will notice that there are wheels placed at different lengths around it. You want the one that will match the height of the blade you wish to grind for a conplete convex, or a smaller one if you are making a Saber grind, say about two-thirds of the height of the blade.
I hope this helps some? Sharp belts are in order, other than that there really aren't any hard rules here. So grind away and experiment to find what works best for you?
Have fun!