One of the most important aspects to producing great tasting and great looking extractions is achieving an even extraction. This is easier said than done. However using the correct WDT tool with the correct technique is a great start. Before I begin, I do have to mention that there are alternatives to the WDT.... if you can swing it. There are a select couple grinders out there if you know where to look (and if you have the cash) that grinds, doses, and distributes the coffee so well that the WDT is no longer required to attain perfect extractions. However, that is whole different discussion for anther day. Most normal people can never afford those grinders, and will require some form of WDT or manipulation of the grounds post grind to get the perfect extraction.
The first step in mastering the WDT is understanding that not all WDT tools produce equal results. I've experimented with just about everything I could find and or make before finally shelling out the cash (including the international shipping cost) for the WDT tool made by Londinium.
WDT Tool from Londinium: https://londiniumespresso.com/store/index.php?route=product/product&product_id=211
For me this tool produced the most consistent results by far. Londinium got everything right with this tool, from the gauge of the prongs to the loops at the end of the prongs, it just works.
Once you have a WDT tool that works well you have to make sure that you use it in a consistent and precise manner. For me, using an extra tall dosing cylinder with completely vertical sides not only was a more consistent method for grinding directly into the portafilter, but was also the perfect guide for producing a consistent WDT. Orphan Espresso makes a great one that I highly recommend, but ultimately use whatever works best for you.
Orphan Espresso - IPANEMA Tall Aluminum Portafilter Dosing Cylinder: https://www.orphanespresso.com/OE-IPANEMA-Tall-Aluminum-Portafilter-Dosing-Cylinder_p_2540.html
Once you have a dosing cylinder / funnel that works for you, use the sides of the cylinder and the bottom of basket to guide you. Move in small clockwise circles, scraping the bottom of the basket and sides of the cylinder, while moving in a larger clockwise circle. *Note - I only recommend scraping the bottom of the basket if you are using a WDT tool with rounded ends similar to what I use from Londinium.*
The diagram below shows the small clockwise circles in red, and the larger clockwise circle in blue. The speed and duration of the motion outlined below will also affect your overall extraction quality. I suggest maintaining a steady consistent speed and taking note to replicate it going forward. I also recommend either counting your blue circle revolutions or shooting for an overall WDT time in general. You'll find that some coffees perform better with longer or shorter WDT times than others, so take notes and adjust accordingly.
The last part of my WDT process is using the Keycap puller with the ends cut off. I will say this right away. I know this looks really strange, and everyone always asks me why I use two different WDT tools. Here is my reasoning behind it, feel free to take it or leave it.
The one downside to the Londinium WDT tool is that while doing a great job of evenly mixing up the grounds it leaves holes behind when you finish and pull the prongs out of the grounds.
To counteract this, I use I tool I had previously tested as my sole WDT tool but ultimately landed in the large WDT tool failure pile, a keycap puller I had purchased off Amazon and cut the ends off. I use this tool to lightly scrape the surface of the grounds and fill back in the holes / damage left in the wake of the Londinium WDT tool. I also use this tool to make sure that my top surface layer is completely level. I know it seems like a standard distribution tool would fix these issues, but I've had more consistent results using this tool before using a distribution tool than without.
In conclusion this is what has worked well for me and has provided me with consistent extractions. Ultimately you should use whatever works best for you.