Wait, Pummelator? No, the mod I found was created by Leo40Story and I found it on the Cave Story Modding Wiki.
Is it any good? Because Leo40Story's mod will never be completed, I might take a shot at Pummelator's mod (if I can find it). Link: https://www.cavestory.org/forums/threads/how-2-mod-cave-story.13797/page-2
It's in this thread https://www.cavestory.org/forums/threads/cstsf-2016-modding-competition-showcase-voting-thread.8187/ It may not actually be good, but it is also pretty informative (and riddled with in-jokes no one will get anymore)
Other than the one in BL I don't really remember a TSC/modding tutorial/guide that really spoke to me. I say this while I procrastinate writing one myself though.