Actually it's slightly different than a CPU, but worth noting.
On a CPU you don't need to spread the paste, you just put a little blob in the middle and then attach the heatsink and it will be fine.
But on a GPU, since there is no heat spreader, you want to make sure the whole core has a thin layer of paste. You also want to make sure to use a paste that is non conductive here, in case you make a mess of it. Arctic Cooling MX-2 will work great.