What do you better luck with against a Gleaming Blissey - Flareon or Machamp?
Probably comes down to what you have available. I have a maxed perfect Machamp and i do fine since Dynamic Punch generally allows me to dodge the gleams, but I just got ahold of a couple of good Flareons so I might give those a whirl (I don't see myself liking them more though).
Those lucky enough to be blessed with a Focus Blast Mewtwo (like my casual friend) needn't worry about Gleam hardly at all. If you have legendaries available, an Entei or Moltres might serve you better (I'm maxing out my Moltres soon and I think it'll give Gleam Blisseys a run for their eggs)