I'm not an expert, but I don't bother doing anything with the corks before inserting them. Haven't had a problem, as long as they're new in the bag. Assuming your sulfite levels are correct when you bottle, the wine itself should be a pretty good sanitizer.
Now if the bag of corks has been sitting open for awhile, all bets are off. I've heard of people putting the dry corks in a bowl inside a bucket with some k-meta solution so that the SO2 offgassing from the water helps kill whatever may be living on them. But a properly attenuated wine should be pretty effective at sanitizing.