In my experience, grind, dose and distribution are critical to excellence in the cup - far more so than tamping. I am much more impressed by the pre-tamp picture in JonR's article - wow, great distribution! Assuming the grind is correct, this distribution coupled with any reasonably level tamp practically guarantees an even extraction. So why do home baristi have so many problems? Let me humbly offer a few amateur thoughts on this subject.
Most "real" espresso grinders are designed for the high production commercial environment rather than home use. Consider the enormous bean hoppers and dosers, and the mods that people make in order to grind one shot at a time. Distribution is equally problematic, with clumping and static creating ongoing issues. The Versalab M3 grinder recently created quite a stir; from what I've read, its even distribution pattern may be more significant than its grind.
When I got my TagEx Mazzer SJ, I replaced the burrs and removed the doser - and immediately had issues with clumping. Clumping caused uneven distribution, which was obvious with a bottomless PF. With the doser removed, it was easy to see the grounds piling up and compacting in the chute below the burrs. IMHO this is a serious design flaw that needs to be corrected (and perhaps has been addressed in the Versalab). We need a grinder with vertically oriented burrs (or some other innovative design) that allows grounds to drop straight down into the PF rather than piling up in the chute. Dosers help reduce clumping as they sweep the grounds around, but it's hard to get an even distribution since the doser vanes inevitably pitch the grounds to one side.
We develop our own rituals to correct these design flaws. Some advocate removing the basket from the PF and rotating it 360 degrees while dosing (from a dosered grinder). Others start dosing while grinding. Some dose into a container and shake it up and down. Others recommend light mid-dose tamps and/or downward tapping, to settle and distribute the grounds partway through dosing. At least one CGer mounted his doserless grinder on a slant board to allow grounds to exit the chute more freely. Ridiculous, isn't it? As users, we should not have to resort to such shenanigans...
Anyway, I have not been able to achieve a consistent dose and distribution by sweeping grounds around in the filter basket with my fingers and hand. Perhaps if I worked in a coffee house and pulled hundreds of shots a day... but I don't. So one day I tried stirring the grounds around with a needle to break up clumps and even the distribution. I know it sounds odd, but it makes perfect sense to me. Not only does stirring declump the grounds, but the needle evens the distribution vertically, all the way down to the bottom of the basket. I simply cannot get this effect with my fingers.
Stirring is just another way of overcoming grinder design defects. After stirring, you can level using the Schomer method, the Stockfleth, or the Chicago Chop (my current favorite). If you want less coffee grounds, stir more to fluff up the grounds, and sweep off the excess to level without any downwards compression. If you want to updose, compress the grounds by pressing down gently with your fingers, or tap the PF gently downwards before levelling - either method will updose with even compaction. Then apply your favorite tamp.
To reduce mess in updosing, a yogurt container with the bottom cut off serves as a handy funnel that sits in the filter basket (see pic posted here
). Dose into this contraption, stir to distribute the grounds evenly, and tap downwards to compact the grounds. Then remove the funnel and level, compressing further if even greater updosing is desired.
Call it a crutch, call it whatever you will, but I have not found anything else that approaches the consistency and flexibility of this approach. With good distribution, I can bang out one espressoporn-worthy shot after another. Granted, this is not recommended for pros in a commercial environment - it's much too slow, and probably unnecessary. But for the home barista, well, at least give it a try before telling me it's a boneheaded idea.