I feel like i might have been experiencing something like HI but its not the same as colors and sounds blablabla like everyone talks about. I see complete blackness, but somehow the blackness sort of…changes shape, or dimension. I really can’t describe it the blackness just sort of changes. It might be deeper or bigger but its still all blackness and still always the same size… I’m sorry its really confusing
I have only recently started trying the WILD method, seeing as the MILD method for me is not always reliable (miss tons of dream signs).
For me it starts out black, then some light spots appear randomly on and off, sometimes blue, orange, red etc. Eventually I see flashes of something, but they are gone too fat for my brain to register what I saw. Then if I hang in there a while longer The flashes turn into items. Not pictures exactly, but more like someone put an image in Paintshop traced it and deleted the back ground, so it kinda floats. For me the images make no sense. Like today I saw quick flashes of a belt buckle, watch, the face of someone I don’t know, etc. I haven’t made it to a scene yet.
Also, I came up with something to prevent the swallowing which unfortunately gets you back to square one. This is gonna sound really retarded but it works for me.
I lay on my side put a washcloth under my face, and do the WILD with my mouth slightly open. And yes, I drool a bit at some point, but that’s what the washcloth is for. If I don’t do this it feels to me like I drown in my saliva and end up swallowing as a reflex. So if you don’t mind looking rather odd, try it, it works. 
I think I know what you mean. It’s not HI yet, but it should develop something like
blackness->blackness with depth (or something like that. what you were taling about, I believe)-> thought images (what kauaidreamer was refering to, I believe. not exactly images, but the impression or idea of an image)->images->full scene
I haven’t gotten that far, so I might be wrong. 
Whenever I get full images and scenes it’s when I kinda wake up during the process.
Ditto here, but I think that’s because my heart skips a beat! So I don’t exactly wake up, it’s more like taking a couple of steps backward.