lol, that is some nice work with only filters.
But like unokpasabaxaki said, patterns are completely destroyed, it shouldn't be too hard to overlay everything with grays and patterns though.
It seems as though whatever you did you didn't keep an anti-aliased format, the lines all look very jagged and sharp. You can see it clearly on the last panel with Amamiya.
Off topic towards the cleaning process but, try and keep borders aligned with each other when necessary. 2nd and 3rd panel are kinda hovering away from each other, lol.
Very impressive work, if you were able to also apply selective tools and fill in necessary grays and blacks than it would really be a nice speed scan. For example the floor and part of the wall in the first panel, most if not all of it should be a clean gray although the scan creates darker areas that could be confused with anything darker.