Another SRS service of some kind will help a lot. I personally use Houhou, which is a desktop application that works a lot like Wanikani. Another good web-based alternative (that I haven’t used myself, though I’m considering doing so in the future) is Kitsun.io. A more specialized one is Floflo, which is tuned specifically toward learning vocab from particular books, rather than just general word lists. All those were developed by people who use Wanikani (and there are threads for each of them here on the forums.)
There are other services that I don’t like quite as much/that are quite dissimilar from Wanikani, other than just having an SRS system. https://iknow.jp/ and https://www.memrise.com/ are two web-based ones. I’ve never used Memrise. I tried iknow.jp, and it was fine but I ultimately didn’t end up sticking with it, since I liked Houhou (and choosing my own vocab to study) better.
The big one people use is https://apps.ankiweb.net/. I personally can’t stand it, but a lot of people swear by it. There are a lot of pre-made decks for various vocab lists, and you can of course make your own. It’s high customizable, but it also takes a bit of work if you want to change it much.