Junkers are notorious for not revealing our sources. There's too many of us, and not enough stuff to go around to be giving away all our secrets. Interestingly enough, we do like to brag to each other about our most awesome finds. We want to show off our stuff, just not tell where we got it all.
When you specialize in certain kinds of items, you get known for having a good selection of, in my case, religious items. You create a bit of a customer base, and eventually you get the question: "Where do you find all this stuff?"
My standard answer is: "Everywhere!" Admittedly, it's a bit vague, but it's also pretty much true. As a collector, I'm more tuned to find the items I collect than someone who is not. Truthfully, they just leap out at me, because I notice them more readily. It doesn't matter where they are. I use this to my advantage as a seller.
Sometime last year, I was hitting some estate sales with another dealer. She went down in the basement and came back up declaring that there was nothing there I would be interested in. I went down, stayed five minutes, and came up with half a dozen framed vintage religious pictures. She was oblivious to them, because it's not something she was tuned into.
It honestly doesn't matter what the item is, someone who collects or deals in that item will be more likely to find it in a general setting. This doesn't mean that it's all sheer luck and keeping your eyes open, however. There are some other tricks that I use in my hunt for Catholic religious items in particular.
It does help to know a little bit about the religious history and
development of this area. Part of my interest as a hobbyist has lead me
to do a lot of reading about the Catholic church in Louisville, so I
use that information when I can. Call it "pre-find" research. I use it to choose my hunting grounds.
Along with that, estate sales in neighborhoods that have been heavily Catholic are a good source. In days past, life was more neighborhood-centered, so many people belonged to the churches in their area. Usually an estate sale near an older church will be the home of a deceased parishioner. Older church members are typically more devoted to having things like images and statues, so those sales are a good source. This is true even if the church has been closed or consolidated with another one. Just because the church moves doesn't mean the people do. Oftentimes, the family will keep one or two items that have a lot of memories, like a rosary, but have no interest in the other stuff.
Another great source for me is to make sure to hit sales in the somewhat more eclectic parts of town. Lots of the "cool kids" are into this kind of stuff too, so I find a lot there. Never underestimate what you can find at a "hipster" sale. Stuff is usually cheap too.
Finally, another no-brainer: look for church-run thrifts and/or sales benefiting Catholic schools, organizations and charities. Never miss a sale run by a Catholic church either! Ever!
That's how it works for me, anyways. For another category of item, the tips might be a little different, but mainly it's about using the knowledge you have to figure out where you need to be.