I recall
@stardustsailor had a situation where a large air bubble in the center of a CXA3070 caused damage to the center of the COB. So the paste can make a significant difference. I prefer to err on the side of using too much paste rather than using too little because you can squeeze the excess out by pressing and the layer will be very thing either way.
I think it was
@Doer that suggested I spread the paste on the COB rather than using dabs. I tried it and it does work well and reduces how much paste I am waste. I have also noticed that Prolimatech PK3 can get thick if the temp is in the low 60s Fahrenheit, so making sure PK3 is not too cold can help getting a thin even layer.
Some diyers are using stencils I believe. Reduces the waste even further, maybe less messy but I do not expect any difference in performance considering that polishing the heatsink surface made no difference and stock heatsink pastes perform just as well as PK3 for our application.
And finally, I have checked to see if increasing pressure on the COB affects the thermal transfer and in every test the result was negative. So no need for strong torque setting on the screws etc.