Thanks for sharing your process and for your questions!
Here's my honest feedback
Arminho wrote:I dose singles at 8 grams (4sec), and 16 grams(8 sec) for my doubles. Confirmed with a scale. Just started with a semi-auto a few months ago, but I am noticing a couple of things...
1) My pucks are never dry. Should they be?
2) My pucks the majority of the time stick to the screen. I backflush my machine after each session with the blind basket.
Ok, 1 and 2 are related to a relatively small double shot dose relative to your basket size. I can see loads of headspace clearance in your prepped basket in the video by how far down below the ridge your tamped puck sits in the basket. Excess headspace makes for wetter pucks and lightweight pucks are more likely to be sucked up against the shower screen when you stop the shot than a heavier puck. Search for the nickel test to set your dose correctly for a given machine/basket combination. That should resolve both of these issues.
Arminho wrote:3) I always have grounds on the side of the basket after tamping, and usually just use my finger to knock them loose, then re-tamp. Is there a better way? Tapping the portafilter doesn't seem to dislodge them.
For this, you either need a larger tamper or you need to employ a "North, South, East, West" tamping technique, or don't worry about it.
I employ the NSEW, technique and follow up with NW, NE, SE, SW to grab all 8 "corners" of the basket. While I don't think it's enough to really worry about, remember that loose grounds above means untamped grounds below... Also, you're putting a LOT of effort into your tamp. It's not hurting anything, but you would get just as good of results just using your fingertips pressing on the head of the tamper rather than pushing your weight straight through your palm. You have better control that way, too. Just press down until the grounds stop compacting and you're good to go. Using your fingertips allows you to gauge how level your tamp is by feeling how the tamper fits into the basket, as well.
Arminho wrote:4) Once I dial it in to extract between 20-30 seconds, I find my shots being just off, whether bitter or sour. And I have a hard time telling the difference too.
Have you weighed your shots? They look like 50-60g pours just from looking at the volume vs the amount of crema in the shot. With your 16g doses, you should be seeing a 30-34g yield. With loads of crema, this can be up to a 2Oz shot, but when the crema is thin, 2Oz gives you a very under-extracted shot and won't taste too grand.
One other thing I noticed in your workflow was a lack of a flush of any kind. While you don't need a big flush with your machine, a brief flush of 2 seconds or so is a good practice to warm the bell of the group and stabilize your brew temperature. As for not knowing bitter or sour, don't feel bad! Once you get shots "behaving" in terms of input/output consistency, raise the temperature, a lot, and try some shots. Taste them. Then lower the temp, also a lot, and taste a few shots there. Heck. Taste many shots at both much hotter temps and much cooler cooler temps. Try and identify which you prefer and why. Then try lots of shots that only take 23 seconds. Lots that take 40. Find out what kind of grind gives you shots that you prefer in terms of flavor.