Nice thread!
I too often have difficulty translating the mental imagery into spoken language, often because the thoughts are broad and encompass many necessary explanatory units of information not easily presented extemporaneously or briefly during conversation.
In regards to the manner one thinks, while alone and not bound to any social concerns, I think in full color video with highly detailed real-world imagery and when necessary, with more abstract visual and physical symbolism peppered in, all conforming to the laws which guide the physics of one's waking conscious experience albeit at a faster pace. I feel the physical forces and am in tune with the known properties and mechanics of the visually represented components of the mental environment, neither needing nor desiring words or any other artificial language to mediate between myself and the raw information that I am toying with.
My mentation involves no words at all when I am alone and not reading or thinking about interaction with other people. Usually I see myself in thought as I do in person (through these here inquisitive eyeballs), and am always interacting with the mental world while also doing something else, often unrelated, in the external world. Earlier today while preparing with HCL a nice specimen of a coral fossil found a few days ago I was experiencing the chemical and physical process unfolding before me, while perfectly linked with my past experiences involving and thoughts while preparing carbonate fossils, my current expectations, the analysis of the choice of my container and acid dilution, the stinging of the hcl which sparked a visualization of the process by which HF enters the blood and wreaks havoc on ones system and the satisfaction in knowing the sting would be the worst result of HCL exposure, the life of the polyp colonies which created and then left behind the structures to be fossilized and then discovered nearly 400 million years later, the visual imaginings of the glacial processes which created the excellent form of the stone, the heavy equipment which caused the superficial chipping, etc., etc. All this and more during about 2 minutes of manipulating and carefully observing the specimen. Contemplating with a visuo-kinisthetic foundation upon which one builds far more complex and organized systems of thought makes it appreciably easier to access information quickly, though not necessarily to express it.
When people talk with me, I must actively visualize what I intuit as both the greater meaning and the supporting events behind the words which are being communicated in a dynamic 3-d context in order to understand. I am weird with hearing spoken language and it can take me a half second or more to process a spoken thought which I am not in the proper mindset to fluidly mesh with the current mental landscape, and will almost reflexively exclaim "what the 'ell did'jou say?!" before the jumbled auditory information takes a shape I fully understand. Words are of no personal utility in terms of encoding the raw data, unless it is a class of information or experience which absolutely requires the use of language. Back-translation for the benefit of others generally takes more effort and leaves out much valuable information, unfortunately.
When reading, the words are translated into a crystal-clear and highly detailed video, or string of dynamic images anchored in memory to other bits of similarly encoded information, at least while the topic being read is captivating enough to demand focused attention. When repeating noteworthy quotes, which are encoded visually, they must then be translated back into words before being shared with others.
When re-watching movies that haven't been seen in years I wonder where my favorite parts of the movie are, and then I realize that those most vivid memories of the movie are the result of the translation and encoding of potent or poignant spoken language into a vivid visual scene, often more memorable than the ones actually presented. 12 angry men is a particularly good example of this, as well as the Indiana Jones trilogy (never seen the 4th and never care to read or know much of anything about it, lest it spoil the pure appreciation of some of my favorite childhood movies).
Words, tactile experiences, and interpersonal events for all of you are certainly not much more than mere triggers of far greater internal personal understanding, regardless of the internal language with which it is encoded. I find it interesting how the variegated people of this forum operate, and are drawn together out of the need for personal understanding, learning, and the general satisfaction of niche-curiosities due to certain shared personality traits.