True, the staff is very on the ball here, something that should never go underestimated.
Raids have always been a go-to for imageboard population growth in the past, and the raid threads we had a few months ago were a lot of fun to boot. Fishing in more places would probably be a good thing as well, though it depends on the locale.
However, whether we raid or fish, we should take care not to poke hornet's nests that are too big for our britches. I'm sure we could have a lot of fun with some of the modestly sized communities, but one too many determined autists could pose a real challenge for the staff to deal with. Or maybe I just really miss those raid threads from a few months ago. I can't be the only one, right?
Advertising I think is doomed to have a limited reach, since I suspect the vast majority of users who'd be into /mlpol/ already filter ads and run script blockers anyways.
Flooding Derpi sounds fun, though the staff there would be liable to chimp out and mass delete and ban before it could draw too many people in. Still, for a fistful of lulz…
As loathe as I am to say this, getting mobilefags connected to /mlpol/ would probably be a good investment. The site has no mobile interface to speak of, which really makes some older phones and tablets choke on the site, though there was an anon who modded Clover for /mlpol/ over at >>>/qa/4241
, though that was almost a year ago and has no shortage of bugs.
Some more subtle callouts to /mlpol/ could work, too. Pic related is a quick little QR test I whipped up for linking straight to mlpol.net. Snuck into the right places, and with codes generated for specific threads here (since they last for months on end), and I think you can see where this is going.