@Andrew-P Hi Andrew, I am going to try to tackle this as an art journaling coach (and less as an illustrator haha).
Firstly, thank you for sharing your experience with this community. I understand that such flashes of imagination can have a big impact on us, and build up the urge of creating, which is a good thing! It is also a very personal experience that only you can make meaning out of it - so bear in mind that any pointers I'll share shall be taken with a grain of salt. Take whatever feels helpful and leave out the rest of it.
I'll group your questions into 3 parts:
Q1. Do I have a chance of capturing this visual flashes exactly as it happens?
Most probably not, and even if eventually you can (I personally have never been able to, but I won't discount that someone might), I think it is most helpful to manage your expectation so you don't get stuck.
Q2. Can I use these to propell my art making journey?
Absolutely yes! Once you are at peace with point #1 you can start to ask yourself the following questions:
A. How did it make me feel?
Then try to make a drawing or painting that captures that feeling (e.g. It makes me feel as if I am floating in space) then you can draw a small creature floating among the stars, even though it is not the visuals that you see, you are preserving the emotion evoked by it.
B. Do I notice one thing that is prominent in this so-called "movie of the mind"?
Try to remember, if one colour appears prominently throughout. I've had a dream where I couldn't make out what happens but I remember the colour green features prominently in it. Then you use that colour as a starting point. Again, remove all expectations that it will be an exact copy of what you saw, and just enjoy the process of creating and preserving this bit of information. Sometimes it may not be colours, but certain rhythm which you can try to recreate in lines or patterns.
Q3. What can I expect from the process of trying to make these into art?
Enjoyment. Maybe a little bit of frustration. Relief. if the visuals have been bothering you, releasing them into art can be a great relief regardless of whether or not you captured the exact thing. What you should not expect is immediate commercial value (though I won't rule it out completely in the long run, think Yayoi Kusama and her dots, that is not the purpose of your art-making journey at the beginning).
Enjoy the process! Learn a technique or two that can help make art-making more fruitful to you (Colour theory? Composition? Gesture drawing). Don't worry about technique "tainting or distorting your voice". See technique as a toolbox that you can use to express yourself freely. Even if you lose some in the grind of acquiring technical prowess, your genuine voice will come back once you have achieved a level where you are comfortable expressing yourself with whatever technique you have on hand, and the freedom of creating takes over. This doesn't mean master-level proficiency. Think of it like being conversant in a language, you don't need to have a PhD in linguistics to comfortably converse in English. Same with the kind of art making that you seek here.
Lastly, think of your Gift not as the final product, but the beginning of creation, just like clay in the hand of a potter, or a beautiful rough marble in the hand of a sculptor.
I hope it helps in some way 🙂