I've had more luck without the charm. My MM projects are taking me much longer than before I had it. I just breed a shiny scatterbug on my game without it, only took me about 350ish eggs. Last shiny i got on my game with it was about 1000ish. l:
I haven't tried any other methods than MM though.
Yeah, I felt that way too, but here's the thing about it though.
Maybe you aren't aware of it yet...
When you start your game, take out your parents and then redeposit them. In Trade Corner, we've postulated that the game has a bug in it where it 'forgets' that your parents are Masuda-capable and doesn't take account of the Shiny Charm when you turn your game off. So when you turn it back on, take your parents out and then put them back in. Of course, you have to be careful with your egg moves (making sure they still know them) with this method, but it works. I've gotten two shinies in three days and I do not have the Shiny Charm.
FYI: Shiny Goomy and Shiny Shroomish ♥♥