I did this using a normal pressure cooker with I steamer insert and it worked great. My steamer keeps the jar out of the water, it gets heated by the stream instead. I used a small mason far with the lid tightened and then 1/4 turn loosened. My weed was dregs of various batches so I'm sure it had partially decarboxylated already. Due to the age of the weed I cooked it for 15 minutes only and let the pressure release naturally. No smell at all from the pressure cooker. The weed seemed a bit moist when the decarboxylation was complete so I tossed it in a toaster oven at 180f for minutes to dry it out. I then added a whack of coco oil and heated it up in an open pressure cooker (boiling water). When complete it had me stumbling while trying to use my treadmill, awesome! For those of you worried about ruining good weed try out your setup with an empty jar and make sure it seals and is dry at the end.