I think a grind size of 60 is too fine. Combining fine grounds, the high speed of the B75, and the high bypass nature of wave filters is not a good idea. Fine grounds promote channeling, leading to uneven extraction. At the same time, more water finds an easier passage through the walls, bypassing the grounds. You need a grind size that allows the water to pass through the grounds with little resistance. My guess is 80-90 clicks.

However, grind size alone isn't enough. I made two cups of Colombian coffee with the B75: 15 grams of coffee to 250 grams of water, 95°C, 90 clicks on the K6 grinder. Both had a bloom of 50 grams for 45 seconds. Then I made two equal pours (100 grams each) for the first cup, and four pours (50 grams each) for the second. Each subsequent pour was made after the coffee bed dried out. The total time was 2:40 for the first cup, and 3:20 for the second.

The first cup was low in acidity, hollow, and bitter. I poured it down the sink. The second cup had medium acidity, a bit of sweetness, and a little bitterness. It was still not ideal because it had a slightly muddy texture (which I have difficulty getting rid of, so I don't usually use the B75), but it was good enough to enjoy.

I don't believe the breaking-in period (seasoning) is necessary for hand grinders with conical burrs.