If you can't wait to prune after flowering or if your schedule doesn't accomodate, at least wait until late winter or early spring, just before new growth begin. And be careful with 'shaping' - Leucothoe 'Rainbow' is a caning, multi-stemmed shrub that produces long, arching or sprawling branches. It is unnatural to the growth habit to trim it into a ball shape. It is suggested that older stems be removed at the base, 1/3 each year, to renew the vigor of the plant and encourage new, full growth.