I think the only way to effectively do co-op, unless you're downtown in NY city, Shibuya, or LA is to use a Line group. I did end up making a second account on my cell phone so that it is easier, but also am only in the RR Line channel, may not be needed if you join the others.
Did my Golden 10 pull and guess it kind of sucked? Ended up with a Hunter King and Oda Nobunaga (non X version) so at least I have three 5* but the rest were really bad 4*. One yellow sharl away from being able to 6* Zeus and after that will be real close to doing Hunter or Oda.