A good metaphor for seeing ourselves in this way is the various states of water. In its frozen state, water is a solid. As a solid it vibrates relatively slowly. It has a hard surface, more like rock than liquid. However, at temperatures above 32 degrees F, water becomes a liquid. It is soft and viscous, and easily conforms to the shape of whatever contains it. If we add enough heat to water, 212 degrees F in fact, it becomes a gas. In this state it vibrates much faster than liquid or ice. Steam rises and expands and takes up much more volume as the same quantity of liquid or ice. We can compare this to our conception of the three bodies human. Our Energetic Body vibrates much faster, and has much different qualities than our physical body, which is solid and vibrates much slower. However, our Spiritual Body indeed vibrates at a level that is much faster than either, and much like the example of steam, our Spiritual Body expands and is not strictly limited to a physical container.
While we can train our Physical and Energetic Bodies through various practices, that doesn't really apply to our Spiritual Body. This is our essence. It is beyond our influence. It is always present and always has been present. Rather than engage in dubious practices attempting to influence the infinite, it is better to work on developing awareness, which really means to direct attention to that which is aware of being aware. In short, we don't train our Spiritual Body. To optimize that aspect of our being, it is perhaps best to acknowledge and live into that Reality. To simply be. And while meditation, prayer, and various types of practices and rituals are considered to be "spiritual practice", they belong to another category. We can't really practice being who we already are. We can only be.
To that end, we can further consider our water metaphor. Heat can be applied to steam to the degree that it too will change state. At temperatures above 212 degrees F, steam is superheated. At that state, it is invisible to the eye. All the water and vapor have been heated out of it. What remains is basically something close to pure energy. The substance is vibrating extremely fast at this state. This energy is used in power plants and other industrial processes. It is extremely efficient because it does not contain any water vapor, which is corrosive to some processes. Think about that. It doesn't contain water vapor, but is still in essence water. Comparing this to our three bodies, what is this fourth quality, superheated steam, equivalent to? The Dao? God? Our imagination? I'm not so sure that matters as much as understanding the power and potential of water, and how that mirrors human existence. Consider that there is something that is beyond what you now call your Spiritual Body, and that that too is not a separate entity anymore than your other bodies are. Understand that, whatever the state, solid, liquid, gas, pure energy; ice, water, steam, superheated steam; in essence water is still water. On an energetic level, and in terms of potential, humans are much the same. We need each aspect of our manifestation to survive. Further, as we learn to work with and train the first two, we become aware of the higher functions. As that happens many of the limitations we once knew begin to fade. We can, in a way, become like superheated steam: powerful, pure energy; attentive to higher realities; and living a life much richer and expansive than the one we lived when we only thought we were water and ice. Most of us just don't realize that yet.