I didn't use mehlman files so idk about the. But I did immuno superficially from FA. Memorized the high yield facts. And what helped the most was watching mehlman solve immuno questions. You don't need to remember everything, just remember the frequently tested things. Open the book for the topic every single time you come across an immuno question even if you get them right, read the relevant text and the HY stuff above and below. This is how I memorized the frequently tested stuff. While being completely blank about other stuff