The easiest way to do this is, I think, by setting up some paragraph and object styles to automate the layout as much as possible, and then use a script to add in the numbers in anchored frames attached to each paragraph.
Setting up your paragraph styles
In my example here, I’ve set up a document with facing pages and some basic paragraph styles – I’ve just ...
I've never heard of or thought about spread numbering before, but why not?
I see (at least) five different ways to do this. Most of them aren't "dynamic" in the sense that if you start moving spreads around, the numbering won't be correct anymore.
Numbering (not dynamic)
You can use a paragraph style with Numbering as in the link you've provided, but ...