There are many opinions on sterilizing casing. I do sterilize my casing materials. I do it in 1/2 gal jars w/filter discs and covered w/aluminum foil in a p. cooker. This way, I can store as long as needed. Since you don't have a p. cooker, you can pasturize yours in an oven. You can still use jars so you can store what you dont use immediately or you can just use a clean roasting pan and bake at least 140F (per Stamets) but I would use a higher temp like 300 or so. This will kill any bugs and most contams.
If you plan on staying with mushroom cultivation, I would get a decent Pressure cooker as soon as you can. Your success rate will go WAY up and stay there. I have used a p. cooker from the start, so that is where my experience lies.
On a side note, one of my friends who doesn't have a pressure cooker, comes over and does his substrate here and doesn't bother with sterilizing his casings or verm and does pretty good. He has a little more contams, but he doesn't mind a few loses.
For casing trays, I like to use the large Gladware containers, painted with a blue rubberized spray called Plasti-Dip. You can still place the lid on for recover and it isn't transparent with the spray.
And yes, you will notice a large increase in yields over cakes, barring any contam problems.
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-ChesterCopperpott-
"Old enough to know better, young enough to do it anyway."