I have chickens, who create quite a bit of poop I can use to grow mushrooms, but I'm not sure how to pasteurize/sanitize it. I was thinking pressure cooker?

I ordered some spore syringes and I'm not sure if i should get premade bags with injection ports or if I should make my own bags. It's the same cost to buy bags and a used instant pot, and I already have coco coir. Once I get some mushroom colonies going I was planning on keeping it going by breaking it up and mixing it with fresh substrate, but I don't want to keep buying pasteurized manure.

How do people do this? I'm very new