If you get good at making flashcards and taking notes while reading, you can probably read the textbook + make flashcards in less than double the time it would take you to only read the textbook.
That would be my strong recommendation.
To speed up manual flashcard creation, you can take notes in a text document and then import them all at once when you're done. That may be quicker than making them one at a time in Anki.
Alternatively, for a lot of stuff, you can use Image Occlusion (take a picture and block out certain parts).
You can search for AI Flashcards + Anki to find one of the many mediocre tools to automatically generate flashcards. This will almost certainly be a bad idea and not help you on your tests as much as you'd like.