There are two megaships in the system, a Sagan class traveller and an Aquarius class tanker, both owned by Lavignys Legion.
If you go to one of these installations and wait about 30 seconds, a raid will start. Pirate NPCs will jump in and the megaship will ask for aid. If you answer the call, just like you would in a combat zone, you will find all pirates lit up in red and local forces in green. No need to go around scanning ships and hoping to find someone wanted like in the nav beacon.
Three waves will spawn, around 20 ships in total. Once you have destroyed all of the ships you should have around 30 mil in bounties, about 8 mil of which are the Lavignys Legion bounties needed for the CG, provided that you brought a Kwarrant scanner.
Around one minute after the raid is defeated, a new one will start and you can do it all over again. Repeat until out of ammo, out of hull points or bored out of your mind.
I've made it to the top 10% of the CG with this method so far. Happy hunting!
Source: https://www.reddit.com/r/EliteDangerous/comments/xmn3dx/since_people_keep_asking_about_how_to_find/