I've always believed that God implants doctrine into us. We know what's true because we have Holy Spirit.
Absolutely. But our perception of truth is always balanced by outer witness, dovetailed with the inner witness.
Paul went to those "reputed to be pillars" to "see if (he) had run (his) race in vain." This in keeping with the principle of "in the mouth of two or three witnesses is (it) established." The reason why there is a Nicene Creed is that we as the household of God needed some parameters by which to establish what is (biblical) truth.
So what we have with SS is the idea that we can ignore the community part and just ehstablish the measuring stick. Believe it or not, we have essentially the same measuring stick.
But no one really does ignore the community part. Virtually no one practices Solo Scriptura. We all have some community that we partake of, and are informed by.
So what is the best method to preserve teaching? The answer is obvious: the text book remains unchanged- but the students require a teacher. The student who says "I believe my textbook, not the teacher" is a good fact checker, but an unlearned student.
But NO ONE practices faith like that. It's three card monte. We ALL follow teaching, even if we switch schools of thought.
Certain members, Like CJ, like to give say that Catholics, for example, don't have scripture as a textbook in their class. He reads their liner notes and teacher's guide and quotes bits to make it appear as if they have no textbook. I'm not certain that he intentionally distorts the truth, but he does distort it.
OTOH, there are Catholic and Orthodox members who assertions. hat Protestants follow only their opinions. Not true, either. Protestants follow the tradition that was given them, until they find something else that makes more sense- just as I did. Raised Lutheran, worked as Pastor in a non-denom, found a teaching that made much more sense to me.
There is not a 'most reliable method' there is truly only one method being used. Human beings read sacred literature and teach it according to their views.
The better question is "what is the most reliable teaching among all the teachers." That is a matter of opinion, but there are elements of evidence.
I'd be happy to explore that:
1. Continuity of practice and belief over time
2. Proximity of origin to the founders and founding documents
3. Proximity to the teachings of those more approximate to the time when the documents were written.
4. Evidence of effectiveness and spiritual fruit
None of these are logical "proofs"-there is no such thing. They are evidentiary elements. For example, regarding #3- when we want to know what the Founding Fathers intended in the Constitution, we read their letters and other writings.
Anyway, that is my reasoned response for which I will no doubt be excoriated by those who deny they have a tradition. They amuse me.