[xkcd-sucks]

"Science" is the iterative loop of observing reality, modeling reality, and correcting the model based on observation. It's how children learn to walk.

Science doesn't require formal training in principle; in practice training in critical thinking is good, and training in specific techniques might be necessary to observe + interpret specific phenomena.

As an aside - Many practicing scientists don't fully understand all the techniques they use day-to-day, and almost certainly don't understand techniques several steps removed from what they do themselves. To understand everything is simply impossible.

Everything else a matter of faith: In the honesty of people reporting results, in the competence of people reporting results, in the similarity between model systems and the "real world", etc. Of course one might apply one's training in techniques to validate the consistency of stuff asserted by other things - people, instrument readings, etc.