I always thought of brainstorming as an activity designed to help people who aren't naturally "idea people"; they have to consciously form connections. Those little brainstorm charts in school seemed tedious & pointless to me. Let's just jump to the end.
Ideas have to flow naturally for me too. They often arrived fully formed; sometimes I just get an image or phrase that is interesting & inspires me to use it exactly as is or as a theme of sorts. I know something is interesting enough for me to do when it keeps "bothering" me. Other stuff just amuses me & then I forget about it.
However, other people's ideas
can inspire me; when you work in art departments or in teaching settings, you really HAVE to be open to collaborative idea-forming. I think this is Ne related because of the interaction involved; it can be energizing to ping ideas around. A lot of times, it can just help to shape & clarify an already existing idea I have. Maybe it's not so much inspiring as refining ideas, combining them with others, so as to make something useful of it all. I get really annoyed when people mention ideas they don't want to explore. I think, "Why would you suggest this if you have no intention of doing it ever?". I think this is Ne too - it's not simply mental exploration, but really pursuing that idea & creating something real. Je types always seem to want to plan ahead, and so they suggest things they never do because they put off planning it - we could have done it a million times over if we just DID it & forwent all that planning waste of time. Although I don't mind silliness - going down the rabbit hole just to see. That's fine, but if it morphs into something really interesting, then be prepared to DO it. I was rather secretly mischievous as a child because of this tendency. My ENFP best friend & I were always blowing marshmallows up in the microwave, burying headless barbies in the garden, or spray painting goofy limericks on the park asphalt. I built a playhouse entirely out of paper once - just to see if I could do it. It was awesome; my mom still talks about it to this day.
I do sometimes
take from other things too; I like looking at fashion magazines for inspiration. I don't copy what I see; I just use it as a springboard & then form something of my own. My brain sort of immediately discerns the base concept & tosses the obvious; a lot of this is Fi-ish too - there's some feeling-tone attachment that says "this is good, keep this, toss that" so you end up with a very vague framework to use. Nothing is wholly original anyway; it's all derivative if you consider it closely enough. I'm driven to improve also, and I think that is a Fi (maybe just Ji) influence. It can be frustrating to know exactly how something could be better but not have the ability to do it, whether financially or talent-wise or whatever. I'm very much a "dreamer", always thinking of a better future.
I sometimes find doing something else that is unrelated to the task helps to get ideas. When I do graphic design, I have to create on command, which is hard when you're not in the mood; so when I get stuck, I take a break. I do something else. Doing something else gives me ideas. It's very indirect & it looks like goofing off

. If I were to map backwards how an idea might have formed, then it might look like brainstorming, but I don't consciously do it. Instead I just focus on other things, stop thinking about it, and wait for some inspiration to strike. You learn these "methods" to harness inspiration when creating is your paycheck.
Frankly, I think most of my creativity comes down to Fi though. I was most creative when younger, when Ne seemed less developed. I had more concentration, more focus on a singular idea, and I was way more productive. I spent a lot of time creating things which mirrored some fantasy ideal I had or expressed my view of how people/the world are, and I didn't even quite know it then. The desire to create to express a hard to articulate concept - that is Fi motivated. I will often get ideas when thinking about what I want/need or some general truth about people/the world, but via some mental fantasy story or exploration of a mood (aka imagination). Wallowing in a (good or bad) mood helps a lot

. Then an idea pops up, and if it's interesting enough, then I'll do something with it.