Don’t really think about where exactly is the location of the channel.
Similar to “breathing through the skin”, I know the body has skin cover it.
I visualize the air through in and out the skin and soon I also have feeling of the air exchange through the body.
As for the other parts of the body, locate the general position of the organ if I want to work on it more. Visualize the energy can pass through in and out of that organ without any blockages. That is my intent for all channels opened for that area.
All in all, I visualize the energy can pass in/out through all area of the body as my concept of all channels are opened. I like to let my body does its own work. For meditation, going into emptiness is easier when I have less matter to focus on.
