Lets see what the creator of lets grow mushrooms has to say about it. Here are multiple post from RR explaining this to people.
You do NOT pick all the small pins when you harvest first flush. If you do you destroy the second and third flushes.
Dunking substrates is an excellent way to hydrate between flushes. Recase the divits where the substrate was damaged by picking.
The number of pins that develop in the second flush has nothing at all to do with the first flush, unless you do something silly like pick them off. Many times, as said above, the pins for the first three flushes all form at once, then sit dormant waiting their turn.
The first flush is over when you've picked the mature fruits. The second flush will begin when the pins you LEAVE in place begin to grow a few days after you pick. Dunking won't hurt the pins. Just make sure you give plenty of air exchange when you place the tray back in the fruiting chamber, so the water can evaporate off the pins.
RR
Mycelium generally sets all the primordia/pins for the first three flushes at the time of the first flush. You'll notice that only about a third or so of the pins grow to maturity. There will be a few aborts that the heads turn black on, but the rest of the pins will be fine and just sitting there dormant. IF YOU PICK THOSE PINS, YOU RUIN YOUR SECOND AND THIRD FLUSH! Pick the mature fruits and any obvious aborts, but leave the rest.
My advice was for cased substrate as well. Cakes are no differnt from bulk grows, only smaller. Never pick pins/primordia between flushes. If so, you ruin the next flush. Aborts will have black heads and be obviously dead. If the pins have normal color heads, they're just sitting dormant waiting their turn at the nutrients the substrate has to offer.
RR
As said earlier, pins that are not aborts are the pins that were set for the second flush. That's the nature of fungi. Often, pins for the first three flushes are all set at the same time, but through a process we don't understand yet, the mycelium figures out which ones to mature and which ones to hold back for flush two and later. Picking them off sets you back.
As for 2nd flush strategy, dunking will tend to initiate it, but it also helps to let the substrate dry out somewhat and 'rest' before initiating second flush with the soaking. Shiitake growers typically remove the blocks from the fruiting area, to allow them to dry in the colonization room at low humidity. This strategy works with cubes too, but you only need to let them rest for 6 to 7 days, not the two weeks we let shiitake sit. By allowing the substrate to partially dry, and then soaking, the next flush usually comes right along. In this regard, we're mimicking nature with warm temperatures, followed by a soaking rain.
In general, you're going to get 80% or so of your potential product on the first two flushes, provided you've initiated them properly. Many growers feel their fruiting area real estate is better served by replacing post 2nd flush substrates with fresh ones to keep the cycle going at maximum. Everyone just needs to experiment and see what works best under their conditions.
RR
This has all been covered many times before. You should NEVER pick non-aborts. It's extremely common for the fruits for the first two or three flushes to be set at the time of first flush, where they remain dormant until their time comes.
You should dunk and roll prior to first flush, and then dunk only after first flush(no roll), and as said above, never pick pins that are not black.
In addition, it's a total myth that aborts contaminate. They don't. Even if they rotted, bacteria isn't a contaminant to fully colonized substrates.
RR
