I think doing the stocks page is the hard way.
You can just designate the cage the orc/goblin/elf is in for dumping via d-b-d and it will flag -everything- in that spot to be dumped. Then after designating go back and un-flag the cage (k-d) so the dwarves don't dump it too.
I build the cage (was under the impression that a cage on a Animal-type stockpile acceptign that creature would not 'pass on' a Dump select to the contents, but I might very well be wrong about that), which means that the cage, while marked, doesn't get to be Dumped.
And while I'm waiting for the contents to be dumped, I connect a lever to the cage (having built it in a place where I can confine the soon-to-be-nekkid enemy, apart from the route 'out' through weapons traps/situations of my devising). When I'm sure there's nothing more to be dumped (have to go into the stocks menu and make sure there are no more D-marked items still, which requires a little extra analysis under Tab if if I've marked all damaged Dwarven socks/etc to be dumped as part of a damaged clothing replacement scheme, or whatavyer) and unforbidden those that were, I can pull the lever and FNU!
I actually can afford to be less thorough, given the deadliness of the exit route, but I really wish I could find out what inventory a caged creature still had on them, as well. But I can only do that immediately after their levered-release. At that point, it usually doesn't matter, though.
(And if I haven't un-
Ded the cage, it of course is now in line to be dumped. As are the mechanisms, if present while making the latest Dumping action. This may or may not be what I want to do, but it's all managable.)