Before WaniKani, there was Reviewing the Kanji. I think it’s still there, but I left it behind years ago as several moderators and … prolific posters in the community were using the forum to perpetuate some very damaging myths about depression, so I was quite happy to find WK where y’all seem cool and supportive and I can learn and reinforce readings and vocabulary along with the kanji (without getting too distracted by “Someone is wrong on the Internet!” in the forums).
Reviewing the Kanji had an SRS that follows Heisig’s method, and I can say it did help me retain my kanji knowledge (I started with handmade paper flash cards and Heisig’s book). It is definitely frustrating to go through WaniKani after Heisig and deal with conflicting radicals and keywords, but I can add the Heisig keywords or radical names as synonyms as they come up (if I weren’t so lazy about it).
A downside of Reviewing the Kanji is that other users can enter their mnemonic stories, and at least when I used it, they were hard to hide (if you wanted to look at your own or the “official” story) and some people chose to use racist caricatures and make up some pretty awful stuff. Which, fine, Heisig does say that the more shocking and vivid the image, the better, but I wish they’d kept it to themselves or that the moderation had been better.
The one thing I’m glad I did with Heisig is to write the kanji by hand. If you write them out, it really helps you to distinguish between similar-looking kanji. If I were starting now, with the benefit of hindsight, I would do WaniKani but make sure to write the kanji out, at least for the first lesson and possibly each time it comes up for review, or each time you get it wrong. (Pro tip: it is more fun if you get a brush pen.)
Also, get a conversation partner. This is essential! You can pay for a lesson, or likely find someone who’s willing to trade English conversation for Japanese conversation. My conversation partner had a great idea that pushed us both out of our comfort zone - she carried on her half of the conversation speaking only English, and I spoke only in Japanese. It was weird at first but helped a lot!
This is also a really great time to take a Japanese class, since colleges all over the world are bringing their courses online. A community college class is a really great investment. A lot of the folks (not here, I’m thinking of prominent immersion “experts” who market their courses online) who are all “I learned Japanese and never took a class!” … actually did take a class, but they claimed it was “boring” or they “forgot everything.” Having tried to learn Italian through immersion without a class, then jumping in to a beginner’s class at my community college, I can tell you it made a huge difference to have a group of learners, some structure, and an instructor who could answer all my weird questions. You can probably get by with a textbook or some grammar videos, but don’t discount the value of a class. Check the community college listings, starting in your home state as they will likely be cheaper for residents.