What should be noted is a good chunk of /co/ saw the show 2 years ago with the leaks. And that's why it has constant threads despite not releasing anything in 2 years, people here actually like it and the ones who don't need it to be heavily advertised to them see it.
Disney isn't going to promote it until Ducktales ends (if it ever does), and that's out of our control, but what you can do is get it known outside /co/. Which is the main concern, because /co/ is extremely limited in appeal (ms /co/ got at most 800 votes, that's all you need to know) and it alone won't get support a show needs >Spread on social media
Of course the most obvious thing, but if you have a limited reach like almost everyone? Make something like a "Legend of the Three Caballeros out of context" twitter, which I don't think exists yet. Or some other sites. Get it going beyond what is known, and it might pop up to people who never heard of it. They love fan interaction, and show without any promotion it has the fans it does. That's just twitter, there's other sites too, many, many other sites. Whatever you can do to shill>Commission porn
Xandra is underrated in the porn scene but people really like it when she gets stuff, and that might get people to know her if random accounts share it and say where she's from. That waifu thread here got some new viewers, and I doubt Disney would care. If not porn, then maybe sfw pictures of the show>Increase knowledge of the show
Let people know about it and make the discussion around it larger then it is now. For example, if you want my opinion the Wikipedia article for the show is pure shit compared to what it could be. Spruce it up some, add many of the references and history around the show there (this was something I wanted to do but didn't have the time for). Or maybe if you're one of the autists on TV Tropes make that page larger. Make it stand up to the length and quality of articles Ducktales 2017 has