When experimenting with your Breville Barista Express, I've found that grind size greatly affects the balance between flavor and extraction time. While the common advice is to grind finer for espresso, adjusting to a slightly coarser setting, like moving from grind 3 to grind 4, can actually yield a more satisfying taste and more consistent flow. One key factor to consider is your coffee beans' freshness. For example, beans roasted about two weeks ago, such as the Alchemy beans by Deeper Roots mentioned here, tend to perform better with a slightly coarser grind. This allows water to flow steadily during the roughly 28-second pull, avoiding over-extraction and bitterness. I also emphasize the importance of locking your portafilter tightly to ensure even pressure and avoid channeling. Adjusting your grind size in tandem with these factors helps achieve the perfect espresso pull. Additionally, each machine and bean combination is unique, so it's valuable to experiment incrementally. Keep detailed notes of grind settings, timing, and taste outcomes to find your personal sweet spot. This approach ultimately makes espresso brewing more enjoyable and tailored to your preferences.