When I install a heat sink on a CPU, I put some paste on the CPU, then press down and rotate the heat sink around to make sure the paste gets spread around to cover all of the CPU die. Then I take the heat sink off to make sure it got everywhere, then put it back on after adding a little extra paste in spots if it is needed. I always try for a thin, but still fully covered layer.

If this TX3 is so thick, it's going to be hard to spread evenly, causing more aggravation than it is worth.