Ok, so I got busy last night.
I went with the idea from onediadem for sealing the top. Paper towels, then soaked in bleach solution. It seemed to be effective, but I need a better long-term solution, as this took some careful balancing and is a bit of a pain.
I upturned my agar half pints as CatsAndBats suggested, but I think I should have done it much sooner. It may not have helped though, as I recall seeing some comments regarding T-TEK having some issues with agar setting and Cats expressed some misgivings about whether my agar would even set. I did get a set mass, but it was extremely soft, to the point where I couldn't even feel any resistance when I was trying to deposit material on the surface. This, combined with the fact that my SAB is not completely clear, plus the condensation forming on the walls, made things very challenging. The addition of BRF and hardwood pellets may not have been the best move for first agar attempt either. It made for some particulates that will make it harder to distinguish any infection. Hardwood tea may have been a better alternative to the pellets.
Here you can see how I hung paper towels over the arm holes with duck tape. I then soaked them in bleach solution. Again, a better long-term solution needed. I had to replace the paper towels a couple of times once the moisture soaked thoroughly under the tape (the duck tape was effective throughout the session and didn't have to be replaced). I decided not to make use of the Sub-sandwich bags. I tried them, but they felt too bulky and in retrospect I'm glad I didn't use them, as I did have issues with available space and the warmth of the room was making me sweat profusely. I was able to keep my hands and arms sweat-free and doused in bleach solution, but if I'd been using the bags they would have been sticking to me all over the place and possibly dripping sweat into the SAB.
Here's the carnage afterwards. Red is from dumping the excess liquid. If I opt for a SAB liner next time it will be a cloth towel rather than paper towels. They got ripped to shreds moving things around. Dental pick was used for depositing sample tissue. Small bowl full of bleach solution for dental pick between jars and for soaking paper towels to keep things wet down. BBQ lighter is for flaming dental pick between jars.
Hoping I was grabbing good Mycelium from these larger shiitake, as they had dried out a bit.
Shiitake Slurry Agar
These shiitake dried quite nicely into little shriveled nuggets on the bottom shelf of the fridge by the time I got to them. I blended about half a dozen in 50 mL of distilled water, then grabbed some small rehydrated chunks with the dental pick.
Some chunks bigger than what I thought ideal, but oh well.
Tree Oyster Agar
This looked like some nice Mycelium pads on the stem bases of some store-bought oysters.
King Oyster Agar
Tissue grabbed from inside of store-bought King Oyster caps. Also did one of gill scrapings.
Now the waiting game begins. Jars have hard water deposits from pressure cooking, so sorry if not the best views.
A note about safety. I am always careful not to mix chemicals. Although you see IPA & Windex in pics and I mention bleach solution, I did not use these different chemicals together. Windex was used for some general cleanup of the work area. Isopropyl was used for wiping down some items before the SAB session and allowed to completely dry. Bleach solution was used to mop the floor in the room used, and to wipe down the SAB and equipment during session.