From my experience dialing in espresso shots with the Breville Barista Express, grind size and dosing are crucial to achieving a balanced and flavorful cup. In this recent experiment, using 18g of La Armonia Hermosa beans and targeting a 36.9g yield over 26 seconds at grind setting 3, I noticed the shot tasted better but retained a slight sourness. This usually signals that the extraction is running too fast, which is why I plan to grind finer in the next attempt. One tip I've found helpful is to watch for shot time and yield during extraction closely. Too fast of a shot often means the coffee bed isn't offering enough resistance, leaving some desirable flavors under-extracted and sour notes overemphasized. Adjusting the grinder one step finer while keeping dose consistent can slow the flow and improve flavor balance. It’s also worth considering the roast date when dialing in. At 19 days post-roast, these beans are relatively fresh and vibrant, which naturally offers more acidity—this could contribute to the sourness if the extraction isn't optimized. Letting beans rest a few more days sometimes helps mellow brightness. Furthermore, consistency in tamping pressure and ensuring the portafilter is clean can influence extraction quality. I recommend testing multiple shots while slightly adjusting just one variable at a time to better understand how each affects the final cup. Overall, patience and small incremental changes are key to dialing in with precision on the Breville Barista Express. Sharing experiences with grind settings, dose, and timing can accelerate learning and help achieve that perfectly balanced espresso shot you’re aiming for.