Advice on cleaning this thing?

So I've had this bong for a while, its cool and hits really smooth. Its got a tripple honeycomb perk, but the issue is that it traps in plant matter. It seems like no matter what, I can't get it cleaner than this. And before you say anything, yes OF COURSE I use warm isopropyl and salt. Added pictures for reference (taken just after my attempt at cleaning), including a rough illustration in case the photos are hard to read.