just apply on one of the 2 surfaces?? the heatsink or CPU?
it doesn't make a difference. I personally use antec silver, very similar to artic silver. They state put a small spread on the HS and a tiny dot (less then a peace of rice) on the CPU. I've also done the spread on the CPU, pea size on the CPU, make an "X" on the CPU, and several others. All the temp reading where within 2C of each other. I personally like the X method.
Currently I have the CM 212+ cooler. I just placed a very thin line on each heat pipe and a rice size amount on the CPU. works fine.