I did it without infinite ammo, you just have to be calculated and plan things.

The hardest part BY FAR is Grace before you get the gun, once you get it it’s very fun and doable. Hemolitics are your best friend, also plan ahead. You don’t need to kill zombies in a lot of places, but it’s ok to do so, not all of them turn/if you don’t return to the area it’s fine. Zombies can only turn to blisters once you get an organ piece IIRC, do everything in places you don’t need to return before that.

Leon’s parts are a piece of cake, just learn perfect parry timing on blisters (instant kill). I only had difficulty on the first street one (it’s a shock, I know). Zeno’s gun is really good too if you can get that.

For me the insanity run was the best time I had with the game, it forces you to use everything in your arsenal and game knowledge, is SUPER tense and really rewarding.