Much easier than it sounds. I would recommend Chris as he's better with a knife and can take more hits, it would also be advisable to play on very easy. You can avoid every enemy except Yawn, a Hunter (if you are saving Rebecca for the good ending trophy), Crimson Head Prototype and Tyrant.
For Yawn simply knife it's tail over and over. The hunter that attacks Rebecca goes down pretty fast, just be careful of it's instant kill charge up attack. The Crimson Head Prototype can be a bit tricky as it's very fast so bring a few herbs. And Tyrant is surprisingly easy if you hit it once then run and repeat that pattern over and over.
Electrifying the giant Neptune shark doesn't count as it's a puzzle and using the rocket launcher on Tyrant doesn't count either so don't worry. Just be careful not to burn any zombies or use defensive items. Set defensive items to manual in the options. I'm not sure if the zombie in the tub that Jill crushes automatically counts so best to avoid that one just in case.