Resistance cords are a great idea. Get a couple of those, attach'em to a bed post or something, and draw your arm back like you would with a bow. Should help out a lot. If you have access to a gym, bent over one arm rows are a similar exersize that would mimic the draw motion. Also, seated rows on an overhead/under machine. Really any arm pullexersizes would do the trick. Tricep workout are what your looking for.