So when it comes to searching, I've got two go-to queries for Google:
For ANG units, just copy and paste this: site:ang.af.mil "upt" OR "supt" AND "apply"
For AFRC units, just copy and paste this: site:afrc.af.mil "upt" OR "supt" AND "apply"
You can swap out "apply" with other words like "submit" or "deadline" and see what comes up! I've found 3-4 boards not listed on GuardReserveJobs.com or BogiDope.com this way; hopefully the more eyes searching the more options we'll dig up! Also, another thing to do when searching is to click "Tools" > and instead of "Any time" choose "Within the past month", so you know you're getting recent results.
ETA: You can also just search by squadron (i.e. "47th Fighter Squadron" AND "upt", something like that) and see what comes up as well! I believe I've had some luck finding boards that way, too. That way, you can target specific squadrons that you're interested in and see if anything comes up!
Best of luck to you all!