Food that's eaten raw results in seeds being released (often left lying around after dwarves have eaten). You probably know cooking destroys seeds. Your text is somewhat scrambled, so it's not clear if you as about workshop seed extraction or state that you already know about them, but seeds are extracted in the Farmer's Workshop and the Still. I don't quite remember what the first step of papyrus making is, but that step also extracts seeds (although papyrus cannot be eaten, "only" used for writing material production).
Dumping cannot specify zones, unfortunately, so you either use a single zone, juggle multiple zones with only one active at a time (hoping the previous lot of dumping has been finished before you switch), or have multiple zones and let DF decide which one to dump stuff in. I haven't found a way to see if there are any dumping jobs remaining, since DF only brings up some of them on the Jobs list, and that list can be empty of dumping jobs even if there are ones outstanding (that will show up later).
I believe there are two major ways to strip prisoners:
- d-b-d over the animal stockpile where the prisoners are kept, followed my manually undesignating each cage from dumping. That will dump all the prisoners gear, but will NOT remove the prisoners from the cages (to "dump" them). Forgetting to undesignate the cages will just get those dumped too, after which you can unforbid them to be hauled back, without resulting in any catastrophes. This is the method I use.
- Using the stocks screen's to dump first categories of things only prisoners have, and then tab over to the individual items to mark those. The stock screen method has also been said to work as a means to rob visitors ("said to" as I haven't tried that myself. Definitely handy if you're about to eliminate a visiting vampire merc, as weapon experts are a lot easier to deal with when not armed and armored, as my ill placed advice once showed that taking them on without stripping them first leads to a significant demand for new coffins).