I used to try to clamp the overlays on but I had problems with them slipping out of place when I applied pressure.   I take a sharp knife and slice all the rubber bands off when its cured.  
I like the toughness and the colors of the sheep horn.  It can be anywhere from white to black and swirls of both.  Sometimes I leave the rough outer layer on the overlay.  That looks pretty cool.
I'm working on the tiller now.  I'm still on the long string.  Everything is looking good so far.