Follow them over time. Do a study.
See how long they stay healthy. See what beliefs each "church" comes to espouse. Note the degree of divergence in the various "churches" and whether their beliefs are consistent or conflicting. See to what degree the Christian message becomes mixed and mingled with pagan beliefs or native culture. That should give you some window on the work of the Holy Spirit.
I think your shouts of "success" and your exuberant celebration of "Houston, we have a church" are a little premature. You're introducing people to the word of God. This isn't the end. It's just the beginning. These people are starting a journey (see St. Paul's letters for all the problems of newly-birthed Christian communities).
Do you intend to simply let them wander where ever the "spirit" takes them, or will there be some .....*cough*.....authoritative follow-up in order to guide them, should they start plucking out their eyes, for instance, so as not to sin? 'Course, I would hate to suggest that you might be imposing some of that Christian .......*Protestants cover eyes, dangerous word ahead*........tradition ..........*all clear*......on these new converts, but I take it there is some form of spiritual accountability and guidance.
I think your shouts of "success" and your exuberant celebration of "Houston, we have a church" are a little premature.
= = =
Evidently God disagrees. He's been confirming with sign's following, just as Scripture teaches, right along from the beginning.
I guess God didn't get the RC memo. Maybe He has that channel on permanent IGNORE.