I'm not sure if there is any special tool that you can use.

What I do is, mark the centerline of the aileron (elevator or rudder) LE then make a mark on the top and bottom surface the distance back I want to go....say 1/4" for example. Then on the tip or end surface I make a line connecting the center mark to the top and bottom mark to get the angle I need.
Now depending on the size of the aileron I might place it on my 1" belt sander/disk sander machine. I angle the surface to the amount I need sanded away. I use the 1" belt and sand away most of the material then finish up with a sanding bar.
If the aileron is a small one I'll just use the sanding bar and take the material down to the lines I made.

Also make sure you have the openings for your hinges made first. It's much easier to do on a flat surface than on an angled one.