My ability to visualize things varies dramatically based on my mood, context, if I'm asleep, and whether or not it's "voluntary". It's never better than a fuzzy, 80-90% transparent image, but sometimes I can "see" color and some finer details, and other times it's just an outline. Involuntary visualization (visualizing something in response to written or spoken statements) is a lot stronger for me than voluntarily visualization. If my involuntary image becomes voluntary (because I try to intentionally maintain it) then it goes away. Additionally, I tend to be better at it if I'm in a good mood than if I'm in a bad mood, and I'm better at it if I'm externally prompted to visualize it ("imagine this if you will...").

The best way I'd describe it is that it's like trying to catch smoke with your bare hands. The moment I try to reach out and grab it to get a better look, it goes away. Most of the time the images aren't in front of me, but are "in another dimension". I'm aware that the image is there, I'm aware of what color things are, what their shape is, what texture they are, but I can't actually "feel" or "see" anything.

Except for when I'm asleep.

My dreams tend to be very vivid. Not like a lucid dream (usually), but vivid enough that it's led me to speculate that my seemingly partial-aphantasia might be less about missing neurons and more about a mental block preventing me from directly visualizing anything (I speculate that you're using the same neural pathways when you're dreaming as when you visualize something while awake).

For me personally, I think a lot of practice is going to be about training my "mental fine motor skills" and learning how to "be gentle" with my mental images so that I can interact with them without immediately dispelling them in a puff of smoke.

Something you might try doing is reading short, basic stories (like children's books) without any pictures, with the conscious intent of imagining what you'd see if you were filming them. Don't intentionally imagine things, but keep the idea that you are imagining things in the back of your head. You're creating the belief that you're visualizing something, which may actually help you to visualize it. This is something that people sometimes have to do when they're learning to lucid dream.

One of the main starting points for lucid dreaming is remembering your dreams; but what do you do if you can't remember your dreams? Well, firstly, start a dream journal. Then, once you've got your journal, notepad, text app, etc open, start writing what you think you dreamed about. You're not "making something up", you're "remembering what you think you dreamed". Your brain is either too dumb to know the difference, or smart enough to understand the intent. Either way, your brain will start to get the message that it's supposed to be remembering your dreams and will start retaining them instead of throwing them away.

Doing something similar might help with visualization.