The phrasal verb bring out means to make more prominent. Cooking something a certain way might "bring out" the flavor. Paying someone a compliment might "bring out" the best in that person, or insulting somebody might "bring out" the worst.
So, if you want to emphasize how learners might become more unsure of themselves when you start using the language, I suppose you could say:
Putting something into practice is a good way to bring out doubts.
However, the phrase "bring out doubts" is not very idiomatic, and it might be hard for someone to understand what you're trying to say without additional context.
I made a few slight changes to your original:
- I changed "putting something in practice" to "...into practice..." (into is simply the more natural preposition, I think, but I'm not sure I'd go so far as to say that "in" would be wrong.)
- I changed "is good to" to "is a good way to" (I think the sentence flows better that way)
A better phrasal verb to use might be bring forth:
Putting something into practice is a good way to bring forth doubts.
The phrasal verb "bring forth" means "to give rise to or introduce". I think that's a little bit closer to the meaning you are trying to express, that when you try putting something into practice, a lot of doubts might suddenly spring up.
One other very natural phrasing I thought of was:
Putting something into practice is a good way to bring overcome your doubt.
That may be a true maxim, but it doesn't say what you are trying to express here.