There are lot questions asked in sci-fi, that genuinely belongs on our site i.e movies and tv. Now,I suspect most of the users might not know that there is an SE site for movies and tv. So how can we bring those users to our site as well?
I don't think there is a reason to start trying to focus on this group of users specifically. The rule with question migration is that if it is a good fit for the site, you shouldn't migrate it unless it is off-topic for that site, but on-topic for the site you're migrating to.
Unfortunately there is a bit of an overlap between our two SE's, but unless Sci-fi makes questions about Movies & Television off-topic on their site, there is not much else to be done other than the usual tweet, share, etc of posts to promote us.
The Sci-fi mods know we exist and I interact with them a bit when I can and they have migrated a few questions to us. This in turn, has brought over some users from there (including two of the moderators, Keen and Gilles)
Focusing our 'promotions' on one specific site might be a pitfall for attracting users because if it fails, that's effort we could have expended on promoting across the board with comedies, dramas, etc