How does transferring between TSA airports work if you need to relocate because of your spouse’s job?

Hey everyone, I currently work for TSA and have been here for about 5 years. My wife may be getting a promotion that would require her to oversee multiple stores throughout Iowa, and we’re trying to figure out where we might relocate.

We’re considering Iowa or nearby states, depending on where her location end up being. Some of the airports/cities we’re looking at include DSM, CID, OMA, MCI, STL, and possibly others in the area.
For anyone who has transferred airports, how exactly does the process work?
A few things I’m wondering:
Do you apply for a transfer through USAJOBS, or is there an internal transfer process?
How difficult is it to get approved for a transfer?
How does seniority work when you arrive at the new airport?
Can you contact the new airport directly to see if they’re accepting transfers?
Are smaller airports like DSM or CID harder to transfer into because they have fewer openings?
How long does the process usually take?

I’m mainly trying to plan ahead in case my wife officially gets the promotion. We’re trying to find a place that’s reasonably close to her Iowa territory while also giving me a good TSA airport to transfer to.
I’d especially appreciate hearing from anyone who has transferred from a large airport to a smaller or midsize airport in Iowa, Nebraska, Missouri, Kansas, or another nearby state.

Thanks!