Yeah I have experience with Hericium sp.
I recommend covering jars on top with 2 layers of aluminum foil when PCing, and wrap it well cause there will be pressurized steam of course, not just dripping water. Anyway you wanna keep filters as dry as possible cause when wet it may be permeable in different ways.
Sawdust bags with cheap plastic?.. not sure if I would do that.. would the sawdust be sterilized before or after? You want proper filterbags if you are going to sterilize.
I have done something very similar to what you describe but i did that with sawdust I pasteurized before I put it in that bag, so it's not really as contam sensitive. Other than that I would really just get filterbags if I were you..
Also if you don't have the means to sterilize properly you probably want to stay away from very nutritious substrates like grains and bran as much as possible cause it will contam very easily. Wood on its own can easily be pasteurized but don't try pasteurizing it with added bran.
Yeah supplemented sawdust is superior but you also need to be much cleaner. If you have limited equipment then maybe that is not recommended for you.. (edit: oh i see you do have a PC and other equipment now, also a glovebox?)
Jars of spawn can be made with LC, grains are good, but you'd want self-healing injection ports in your jar lids.
What jars do you have that are actually waterlogged and colonized?
No, people normally don't use BRF and verm as spawn like that.. it's not ideal.
Are you planning to keep using liquid culture long-term? Are you planning to use it to make spawn or to inoculate wood immediately?
I have access to sawdust in similar ways, also I have recently discovered how great pasteurizing wood can be (for active woodlovers but i wanna use it for gourmet / medicinals too now). It's also smart to buffer your substrate to keep contam away, by the way.
Another thing I am wondering about is colonizing unsupplemented sawdust first, and then when it is done, adding micronutritional supplement like bran in a more concentrated form and mixing it through without really having to worry about it contamming before it gets colonized?
You're not quite there yet but when you are fruiting, keeping CO2 down enough to get compact fruits may be one of your bigger challenges. I don't think you should underestimate the value of setting up a proper fruiting chamber, one that has really high humidity, low CO2 and is at least a bit clean and protected from filth.
GL