Thank you Daniel. I used to build and fly wood remote control airplanes. So I have profiled many leading and trailing edges.

I set the wings on my work table, and put sandpaper on a block, but do not let the sandpaper go to the edge of the block. That way I can keep the edge of the block on the work table surface as I sand across the edge of the wing, all the time maintaining the same angle. Then I can change the angle as required to get the final geometry. This way the work surface controls the height of the block and keeps it parallel to the wings top to bottom, and the wings themselves keep the block parallel side to side. Then there is only one variable left, and that's the angle of the block. If you keep the angle consistent, using the wings and work table surface as guides, you will have a very consistent leading or trailing edge.

Then I hand sand the leading edge corner by wrapping the sand paper around the edge and sliding the length of the wing.