Don't worry, it's not a stupid question..
Automobile manufactures have always blown air INTO the radiator from air that is outside of the vehicle.
So following this concept would prove very logical to blow the coldest air through the radiator, either blowing in either direction but not in a suction manner.
In other words, make sure to blow into the radiator/water cooler as opposed to trying to suck air through from any side. Your results will be greatest if you are blowing air through the radiator, and exiting the hot air OUTSIDE of the case somehow.
Remember these rule of thumbs:
1) Blow, don't suck through the radiator.
2) Ensure that the air going through the radiator (which is usually warm to hot), is exhausted outside of the case, rather than blown back in.
Hope this helps.