To answer your question on how to use BA to assist making sermons, first one would have to know, in general, what is your philosophy for writing sermons. I certainly do not use any of the ideas set out in the main textbook on preaching at the seminary I attended.
However, I'll take a stab at answering your question. First pray to the Holy Ghost for a topic, even a very braod one that can be narrowed later. Then, use BA for searching Bible verses and commentary on the topic. Assemble a lot of verses/comments on the topic, and then, pray on what the Holy Ghost wants you to say. You must use inspiration, but having a lot of material at hand helps the process. At times, you may want to look at the parallel bible feature to consider variation on the verses. I think this process will stop being dry and empty and provide support.