Umm I said use kechtup as the layer. Some thermal pastes (like MX3) are so thick I don't think you can hand pressure enough.
Anyhoo. Pacing the CPU on glass and looking up through it or a long razor blade across the top of the CPU with a flashlight shining through the crack tells you a lot.
If it's your first CPU your checking, it doesn't tell you much at all tho, it's learned by experiance whats bad/good.