Or maybe limit new users ability to post at first without long standing members (say 500+ posts or 3 or more years a member) vetting the post. I'd be happy to look at a new post when I come to the board to judge if it is spam or not before seeing what's new. It would only take a few seconds and it'd be for the good of the board. I suspect others would do that same. You could even make it a volunteer new member post review group. Until the new member makes a set number of legit posts. Say 25 or something. It would take that burden off the staff as I am sure they have plenty to do already.
I can't imagine a spammer would take the time to post a bunch of relevant posts to be able to drop a spam post.
After some searching around the new admin panel software and some online research, I think I found a way to cut the spam down, I hope it at least slows a lot from this point.