How does the duty position search work? How can I volunteer or request for an overseas (Korea or Japan) duty station?

I never recommend people use ACT to look up positions because it's never accurate. Most of the time those positions are filled or being filled already. Plus, there is no way to actually take an assignment from there. You can sometimes volunteer for an assignment through ASK if they haven't shut that down yet.

SFC (Join to see) - I was told a long time ago that ACT uses duty assignments that were created by HRC and may or may not be planned to fill within a short time frame. However, I mentioned it because it's always good to know what (in theory) is available in some form or fashion.

SSG (Join to see) the assignments are built in EDAS which is a live system, those assignments can be filled or canceled at any moment in a day. ACT is more like a snapshot of the assignments a few days prior. The ACT assignment finder was an idea that never actually got off the ground. It was functionally replaced by the ASK Assignment volunteer section that actually does display open assignments to fill and actually does generate an assignment request to the branch manager. However, these days with the enlisted marketplace opening, assignments are mostly handled by Career Counselors if in their window, or the enlisted marketplace if not