Just got em...never used either brand. Should I cork em?

I've never had a need to with the Astra, can't speak for the Iridium
Absolutely correct!With the Iridiums, a very light touch simply worked.
imho corking is something that is completely unnecessary...
it is a waste of a blade by 'dulling down', or 'dumbing down' a blade. Just use it for a few more shaves and it will become dull naturally.