Best way I know is to remove the H/Sink and fan complete with the proc.
What I use then is a wall paper stripper blade VERY CAREFULLY between the proc and fan gently apply a little pressure on all four corners in turn to break the hold. I DO NOT GUARANTEE THIS WILL WORK FOR YOU, ITS JUST THE WAY I DO IT.
Again carefully once they are apart I clean off the pink crap with a special chemical I have.
When u put the new grease on the proc, only put the size of a matchhead on the chip itself.
Spread it out with a small screwdriver over the chip to get a thin even layer.
Refit proc, heatsink and fan, clip it down and GENTLY move the h/sink from side to side until u start to feel a slight resistance, THEN STOP.
Reconnect fan cable and away u go.
Go into bios and run computer for 10min watching the temp.
I then use and endless loop program in Windows to load the proc to 100% for another 10 min, keeping an eye on temp in a windows monitoring program.