The key is continuous focused attention. IMO
I’m working my way through the Harry Potter canon in Spanish - nearly finished the 4th book - and I’m seeing fewer yellow words on the pages now and sometimes I even get caught up in the drama so much, the paragraphs flow!
I have been adding common verbs and nouns that just don’t seem to stick to an Anki deck and that helps immensely. A recent example was “salpicar” to splash/splatter/speckle - a tough one to get a handle on.