Are there specific supplications or methods for guiding an unobservant person who grew up in a non-Islamic country, and for whom there is hope of reform?

It is permissible to supplicate for a person's guidance and rectification of their condition. As for advising them, it is recommended to do so with gentleness and kindness, to endear oneself to them with good words and gifts, and to firmly establish the meanings of faith in their heart by reminding them of Allah and His names and attributes. It is also beneficial to explain that obedience benefits the servant, that this worldly life is fleeting, and that the afterlife is the recompense for deeds, while encouraging obedience to Allah by mentioning the reward, and warning against His punishment. It is also recommended to seek assistance from reliable books, tapes, and websites that soften hearts and call to the Sunnah.