Usually, I report low/spam post or not adding much on the discussion and to do that I hit the "Report to moderator" button and on the specific page I usually put every reply that deserves to be reported to "Open link in new tab" so that my reporting will be at ease, and not waiting anymore to wait until the report succeeded. I guess if there are enough posts that's been reported what I observed is the mods delete that topic onto trashcans.
Edit: Just report the 14 pages with spam replies, at the moment it still bursting to new replies so I'll just stop with there until it will be handled. That makes I have 250 unhandled reports and takes me about 55 minutes, hope mods will take action later on.
No need to report all the replies it will be time consuming task so better hit the report to moderator of OP at the thread and ask it to trash due to using bumping services.