How does buying gold and then selling gold prop up the dollar?
when gold goes up... the dollar goes down
when they know the dollar is going to take a hit, they buy gold at the end of the day (NY) and dump it the next morning, pre-open, for a major loss (they don't care as it's phoney money they just printed). this helps offset any bad news
they figure a 3-4% swing is normal and if they can push gold down 3% it'll about even out the next day.