Every Christian religion has its distinct culture.

Very broadly, religions that interpret the bible literally are most immune to rational argument. They explicitly assert that the word of the bible and the tenets of their faith have authority over empirical evidence and reason. Other religions explicitly submit themselves to rational argument and intellectual interrogation.

I think the real challenge for conversion is the latter case. You will not win them over easily, because it is likely they have already considered rationalism and have sophisticated arguments against it. The arguments lean along the lines, "I have the same premises as a rationalist, except that in addition I believe that that there is a source of knowledge beyond what is empirically observed, and my religious beliefs begin where rationalism ends".

With an explicitly irrational religion, I imagine (with no field experience) that you can make a lot of head-way just by teaching critical thinking. On the other hand, pulling from real life, I do not understand how a friend of mine that believes in Creationism was able to get a PhD in cell biology with no crisis of faith. So there's something interesting going on there.