Well, I was playing around in the shop, tillering bows and thinking about a better way to decide where I needed to scrape and made the gadget below.
I took a 6" long piece of 1" square scrap wood, drilled a 5/16" hole in the middle for a pencil and a 1/2" hole just deep enough over one side of the 5/16" hole to tap a 5/16" nut into.
Screw a stubby point pencil into the nut and you are ready to check tiller
I run the block up the limb to get an idea where the limb is bending the most then set the stubby pencil tip almost where it is touching the limb and run the gadget up the limb making sure it is centered. Several passes up and down the limb mark the the stiff areas perfectly. The gizmo shown below is an earlier version from the one pictured above with the nut tapped into the hole. Tapping the nut into block was Daniel Willoughby's idea.
The end result are nice lines just where you need to scrape. The lines tend to get darker in areas that need a few extra scrapes. I only make round belly bows but have found the tool works equally well on flat belly bows.