This.  You should apply the thinnest possible coating.  The purpose of heatsink compound is to fill microscopic gaps between the CPU's cooling surface and the heatsink, and more is not better. In fact, it just gets in the way of good thermal transfer.
If this makes you think you should re-do it, Windex is good for removing old compound from the CPU and heatsink.  I usually start with a BB size drop and spread as thin a coat as possible it on the chip's cooling surface with my index finger.  Then, I mount the heatsink on top of that.
Windex removes heatsink compound from fingers, too.   
 
In 
this thread, last month, others and I gave similar advice, and the OP reported that his CPU temperature went down 8°.
You may also want to check the temperature limits in the CMOS to make sure they're right for your CPU.