I can speak a couple of languages that I don't use very often, I personally just make sure I watch a movie/tv show/the news (the news is the least helpful tbh) in those languages once or twice a week. The article suggests Netflix, but if you're not dealing with one of the more common languages, I've found that a lot of countries have their own streaming services you can use.
I find news helpful for weak languages: read strong languages first, and then there's already known context for the major stories when approaching the weak languages.
The languages I speak have pretty big differences between the formal and the actually spoken language, so watching the news in them has never been that helpful, because I pretty much never need to speak the language spoken by newscasters. My problem is also just that I need to keep up my exposure to the language so that I don’t forget, which requires a bit less effort than the OP went to.
