Best method for making selection for "brush" layer for Electricity Photoshop Action

I’ve been trying to find a way to get an accurate selection using the brush tool but have not found a way to use the “select subject” to help. The instructions are to create a new layer called “brush” and then brush the subject, but doing it this way does not allow me to get a good sharp edge selection of my subject. Maybe I am just missing something. Any suggestions?