I did the same for GG: As soon as I had Lumi and IG86 maxed out I spent 800 GW currency to get 10 shards. Then I'd have my 3 shots on every hard mode with the same two characters. Then once he was maxed, spent arena currency on 88... and even now EVERY cantina battle is spent getting either surplus 86 or 100 shards. It took me about 6 weeks. I've got a few other 7* toons now so I'm getting 5 GG shards every two days. I'm 15/65 for his 5th star. It's a slog but he's worth it. Just be sure to have 3M creds, several thousand training droids and at least 50 purple ability mats (and about 15 Omega) once you've unlocked him... ("_)