What are the best methods of study and practice to achieve complete fluency in Japanese, and be able to understand, speak, and read and write their wonderful language just as competently as a native speaker/reader?

I am still in the "understand a lot, but not enough yet" phase: I know maybe 1000-1500 kanji, am familiar with most if not all the grammar points enough to decode things relatively easily when translating written Japanese, and believe the priority to advance from here is probably to tackle mastering the kanji so I don't keep hitting an unknown kanji while reading.
What I've done so far that made sense to me:
Kana Script
I learned the kana scripts (hiragana and katakana) first.
There's at least 2000 basic kanji needed to get by and more like 3-5,000 I think as the norm for full fluency. (In Chinese there's even more, but Japanese is a little easier on Kanji because of using kana alphabets.)
Grammar Points Overview
I did an overview of the language's grammar points until I'd compiled around 1-3 example sentences (nothing too fancy) for each grammar point to give an applied example.
(By the way, some people don't like thinking about grammar, but I also am the type who struggles to understand what's being talked about when grammar points are discussed in the abstract, but with applied examples it's easy.)
Expanding on this a bit: There are a lot of grammatical particles and also many ways they conjugate verbs in Japanese, as well as a completely logical yet totally different order of words when forming sentences, so to me grammar overview and then having my book of grammar points is useful.
(I can theoretically see "winging it" in favor of deeper immersion and engagement with maybe Spanish, but not Japanese, personally.)
Translation exercises:
I like to translate small fun pieces of material into English and understand the underlying structures (and also learn vocabs this way).
This isn't just because it's fun: To me it's the best way I can think of to get applied practical learning and also something memorable to anchor what you've learned.
(An even better way might be to have a well-paid tutor continuously pushing you forward, giving instant feedback, and stuff like that, but for self-study this is what I do.)
By translating little things you like (whether its film clips from my retro macho action movies with Sonny Chiba or Bunta Sugawara, or maybe animes for the many who like that, or mangas, or even Japanese Twitter), it anchors new vocab and applied grammar points to something really memorable.
A lot of language programs and apps have practical stuff like "My girlfriend's apartment is on the 13th floor," but it's harder to have generic example sentences like that stick, even if it's objectively valuable for its practical value.
Kanji learning:
My personal preference is to first master the "radicals" (sometimes called "primitive elements") that Chinese traditional characters (and therefore Japanese kanji) are composed out of.
That way, even if there's no particularly obvious reason why a radical is part of a given kanji, you can at least say "oh, there's the radical for 'power' or 'sea' or 'sun' etc" instead of just seeing the components of each Kanji as some random mysterious symbol.

I'm open to suggestions from there, but I like the book series "Remembering the Kanji" that links together and introduces groups of related Kanji, while coming up with more or less mnemonic-like stories or imagery to make them memorable;
Even if you don't want to go with the suggested 'story' concepts the book comes up with, the delivery of thousands of Kanji in a sequence by linking together kanji with related elements is (I think) really helpful.
* Here's one for you Japanese students, by the way: Do you hand write kanji at all, or only learn via recognition and computerized typing?
Speaking is another thing:
I'm not focusing on that much right now, but I can say Japanese women are often open to wanting to practice English they're studying, and many don't mind at all if that was theoretically a gateway to feeling you out for a potential romantic/etc relationship either.