Yes. That's actually the method I use, I had forgotten it was from his PDF, I thought it was in the JoS somewhere.
You might not need that much time (he says 10-20 minutes) to get into a deep trance, depends on your skill with trance.
I'd recommend doing the Summoning first, and then when the God is there, do the invocation. It might take years of spiritual advancement to get to the level of being able to invoke them. And some people have barriers up due to a subconscious feeling of discomfort of the thought of a God entering into them. Invoking is a very personal thing to happen. You need to trust Them, and trust that they will not invade your privacy.