Heres something I do when it comes to getting toons in different shipments. We'll use the Jawas, since I've resently gotten them (except the Jawa Engineer) to 7*. What I do is take 1 month, and do nothing but save resources. I'm talking like uber savings. Your daily challenge says train a character? Get that 1* training droid, and use 1 of them in any toon to minimize the credits you'll be using per day. Same thing with mods, just upgrade it once and you're good. So after your month is over, and you have about 30k war tokens, cantina currency, squad area currency, and you have a lot of Guild currency, at every daily energy refresh, go to each shop, and buy shards for each character. The key to doing this tho is that you HAVE to stay on top of it. Set your notifications on for the game so you can see when the refresh comes. Or memerize the times your energy refreshes through out the day.
I counted the days, and on Jan 1st 2017, I started my grind for my Jawa team, and on Jan 15th I got all of my Jawas (except the Jawa Engineer) to 7 stars. Took me about 2 weeks.
Now of course this method is very very situational, but it works.
Another thing you gotta remember is that this is a game that REQUIRES patience, and it's meant for you to stick around as long as the game is around. ALSO remember too, all of the chromemium exclusive characters we see in the game, will be eventually put into a shop or put into a cantina node. I mean look at Lando. He has two nodes in the cantina, so they can easily just swich one of those out with a newer chatacter. Lando aint the only "Multi-node-shard-grind-character" in the game as well.