the greastest "tool" devotees have in preaching is the MAHA-MANTRA itself. unless one is properly qualified to preach, inaccuracies may occur in context...but we need no understanding of the language of the maha-mantra to chant and sing the glories of the Supreme Personality of Godhead. Of course once someones hears the mantra they might become inquistive as to what it is, what it means...then this opens the door for further explaniation.
Remember people can't walk into Harvard and ask for a diplomia, no, they must attend years of schooling, excel at their grades, apply then commit themselves to vigorious studies to achieve this goal.
Self-realization is the same way, you can't understand the nectar right away, you have to start off slow from the beginning and advance from there...
and the MAHA-MANTRA is the most beneficial way to start on the path of self realization.