Start with the general shape using your blade or like I recommend a razor plane.
Once the general shape use 80 grit paper to get it to a rough shape. Then work
your way up to 150 then to 220. Save the higher grits until you are ready to cover.

When making a round shape that is consistent I sand back and forth and move the
block from one side to the other forming the round shape (I cant explain this part
very well). Make sure not to stay in one place too long, if you do you will have a
flat spot.

Another neat tool I recently invested in was the multi-sander from Great Planes.
There is a contour for the leading edge of a tail surface, a triangular contour and
one for a leading edge. The leading edge part is only valuable if your leading edge
is that contour.