1) Start a campaign mission or Resume campaign
2) Hit guide button and exit to dashboard
3) CHANGE RESOLUTION (720p, 1080i, 1080p). Example, if on 720 change to 1080p or I, if on 1080p change to 720p or 1080i
4) Start a new mission (do not resume game)
This works for me and should last 2-5 missions before the grain glitch re-appears.
I've tried exiting to dashboard and starting a new mission without changing resolution and the glitch remained.
Post if it works for you.
(250 gig Slim Model, HDMI, INSTALLED)
WE WILL REMEMBER