You mean, like, kill them DEAD? Make some fresh cuts on the bark and top of the stumps, and paint them immediately with Ortho Brush-B-Gon. Repeat: immediately. I would give them several applications.

One enhancement on Whitecap's suggestion from the stump removal folks is to drill some holes in the stumps and fill with the herbicide. 1/2" holes seem to work well; smaller could be okay, but will offer less surface (contact) area and may be harder to fill depending upon the viscosity. The trick on hole depth for shrubs is to avoid drilling all the way through; you may waste a hole or two figuring this out.