Jack's directions for gluing patches are a bit confusing— oriented towards patching a raft or cat tube on the river where you need to let the adhesive dry and then reactivate it with heat.
For dry bags I've been using Tear-Aid tape, which is a lot easier to apply and still quite effective. I rough up a bit around the punctures and clean with MEK, let dry for 15-20 minutes, apply the Tear-Aid patch, then repeat for the other side.
Two kinds: type A for nearly everything. Type B for vinyl (which I assume includes PVC fabric). Here's a link for Tear-Aid tape:
30 Foot Rolls