Anyone else have any more ideas?
Don't be afraid to make yourself known and promote yourself on generic wargaming groups and 40K groups. 40K is still the largest wargame around, and since it contains a huge number of players, it also contains a huge number of people who play more than one game. Tap into those people who have Armada as a 'side' game and get them involved.
Also don't be afraid to use sites like Reddit. Reach out to your cities subreddit and see if anyone is interested or knows someone who might be interested.
Fliers in local shops and related shops (comic shops, video game shops, etc) might be a good way to reach people as well.