Here are some resources I follow. These are not really USCCA sources, so I apologize for going off topic.
Sheepdog Church Security Training Academy (the website was already referenced). They do a church safety member certification course for somewhere around $90 to $100. They offer group discounts and season priced reductions as well. It’s pretty good. There is a lot of review if you are into this stuff, but if you have folks who’ve never thought this stuff through, they will learn a lot. I took the course and it was worth my time. I’ve not been able to gently convince my team to take it. The guy who runs this site has a YouTube channel. He’s an Iraq veteran who did military police work for some of the highest profile prisoners in Baghdad.
The Faith Based Security Network is worth looking at. I’m not a member. I did attend a church security seminar at which Carl Chinn presented (who runs this site) along with Jimmy Meeks and David Grossman. This seminar was basically why you should do something and how you should get started. It looks like they are still doing these seminars. See here. Carl Chinn tracks incidents of violence at faith-based property. His book, Evil Invades Sanctuary, is worth reading. Carl was involved in a hostage situation when he worked at Focus on the Family and was also involved in response to a church shooting at a mega church in Colorado (Sorry, I forget the name of the church. No disrespect intended). His book addresses this.
Another good source is Worship Service Academy. Once you get on their email list, you get a lot of emails. So I honestly don’t read through much anymore. There is also a podcast here (for Apple).
I would also recommend reaching out to your local emergency management folks in your state or county. Our county department of emergency management provided a free of charge multi-session training module specifically for churches. They did CPR, Stop the Bleed, Active Shooter, general emergency management, and they provided a ton of resources. This included an app just for churches that provided a ton of resources.
Your insurance company is another treasure trove of information. For example, here is the church security section of Brotherhood Mutual Insurance Company’s website. (Brotherhood is the third largest church insurance company. Church Mutual is number one and provides some resources as well, but since we aren’t insured with them, I’m not as familiar.) This page of their website lists some trainers that they recommend.
Another source of good information is Church Law & Tax. This is the nation’s foremost resource of legal and tax information for churches. Here is their search results for the word “security.”
Everyone on your team should watch/listen to David Grossman’s seminar on the bulletproof mind. I have listened to it multiple times and saw it in person. It’s time to listen to it again. It’s 3 hours, 20 minutes long. I believe the USCCA marketed and sold this as a video series at one point. Highly recommended.
Speaking of Grossman, here is his Grossman Academy. I’ve not taken any of these courses.
Another reference is this book: Pistol in the Pulpit. I’ve never read it.
Personally, I am not sure that church security is super specific to churches in many ways. I think a lot of the self-defense knowledge applies universally. So, anything self-defense seems to have a church application in my humble opinion.