I have a 23 qt presto pressure cooker, but I thought I could only fit 4oz jars on top of quarts. Will have to double check next time as that would speed up the process if I can fit pints on top too. I have 4,8,16,32 oz jars so I can stepping up using sterile wort.
I was wondering about the lining of your vials. Looking for new vials, my first vials had a rubber one and the lining came off of few after a few uses. Found out I could not easily find replacement caps. The last set I bought had a different kind of cap from the phenolic type I was using. I was a bit nervous at first but I like the idea of non phenolic cap now so that I can smell if a clean yeast possible got contaminated.
My first batch of slants I allowed the slants to dry out before sealing them up, I had a few bad ones and I think some contaminated slants. Now I tighten the top as I pull them out of the canner jar and tape up as soon as the agar is set. I store upside down to aid draining the condensation.
It is bit of work but it is cool to bring a sleeping vial back to life.
I know making starter is not difficult but man do I like grabbing a jar of wort and be done.