Hi ProudGM,
I've found nicotiana pods to be quite sticky on the outside even when dry. The seeds like to adhere to the pods. So instead of trying to collect pods, I take a baggie right to the plant, tip the pods in, and shake the seeds out.
Petunia pods can be picked before becoming really dry and wide open. Leave the pods in a bag to dry more and the seeds will come out easily.
Hope this helps,
Remy