I basically apply the Testors cement by placing the two parts together, and touching the brush to the joint/seam. By doing that, the model does some of the work for you, because the seam has what is called "Capilary action" that allows a liquid to easily flow along the joint for a little bit. Just touch the brush to the seam about every inch or so, and that sould do it.
I've been using the methood ever since I started using Testor's liquid cement, and it has worked every time.