Ok, your question is correct. It takes some time
You can start by looking at a fair amount of sample agate, then Ravenswood, Alley, (you'll find many in the forum) as well as Christensen agate.
You need to carefully observe them many times, until you notice differences in structure, from each other.
You will find that many Champions may resemble Ravenswood, just as some Ravenswoods may be similar to Christensen agate. Alley's tend to be Flemish in their swills, not all of them, but many, hence they stand out from other companies.
Some Champions (opaque and translucent) were made to remember Ravenswood, with a similar structure but certainly a little different.
You will notice the differences between Ravenswood and Christensen agate, although some are impossible to distinguish (I own one still pending, seen by competent collectors) both in color and structure.
generally, the christensen agate swirl is rather short, fat and powerful (sometimes with some precautions, namely: parallel ribbons, turkey head, ram's head, tunnel, and so on) compared to all the others from other companies.
Colors also matter a lot, such as the white of cac is very shinyng, almost dazzling and many times uv, as well as the syrupy glass (gel type) always of this.
Size can also count at times. If it is rather small 9/16 it is easier that both champion and ravenswood, if it is more generous in size, easier Ravenswood than cac, but perhaps here I am exaggerating, as a little all the companies have made various measures, some more and some less, someone correct me then .... LOL
With time I am sure that you will make a scheme of all this and with a little experience and eye everything will be easier, although (as I said above) with swills sometimes it is very difficult to identify them, if not even impossible. (this applies to everyone, even the most experienced)
Many times, like all of us, you will have sensations for a certain marble, but NOT 100% certainty right and especially with these swilrls!