My experience accords with all the posts above this one: my espresso improved when I began using this technique and I am grateful to the OP for having invented and shared it. I do, however, have a question. Why does it work?

I've read that it fills voids in the dose and that it breaks up clumps. Is that accurate? Are there other reasons?

Matt

mathof wrote:Are there other reasons?

It could be difficult to prove exactly why, but another reason may be due to mixing finer and coarser particles together such that there aren't large areas of unequal distribution - this thought has come to mind after finding that a small whisk works better for me than a needle despite still needing a shake afterwards to level.