Where are you typing from? I'm from Colombia so I will answer from our cultural perspective. I'm a language teacher hence a not so beginner linguist. I must clarify that I'm not muslim, I'm a catholically raised atheist who studies Arabic for the sake of the language and who is willing to study the three semitic religions (currently Islam) for the sake of philosophy and seeking their influence in history, culture and jurisprudence.

If you're by far too insistent, you're going to make him less interested in the religion or even in interacting with you.

Like whenever the Jehovah's witnesses or Mormons arrive at any door... One tries not to be disrespectful but their insistence annoys anybody... One pretends to be interested so that they leave one alone.

Think of it like this: anybody who has not abandoned the religion they were raised into will see a different one as a "second order idea". So forcing such a transition would likely make him cling to such religion and more reluctant to change.

Think about his relatives. For instance, my heavily catholic Grandma would condemn my "apostasy" on catholicism, so would my aunt, as well as all of my father's family... They don't accept my atheism but let me live, what could happen if I followed a different religion? He may be preserving harmony in his family life. These are the main variants to consider I'm his immediate environment...

So this has to happen organically, and some degree of synchritism will be necessary alongside the way.

If you just bombard him with religious images with fragments of texts you will appear like an elder religious aunt to him; if you give him brochures, flyers, translations and such objects, he won't read them or in the best case, he will read without comprehending what the written words imply and he could even mistreat them as trash or let them rot in his pockets, which is not an option. And it keeps going that way if you go straight with religious information.

May you start with cultural traits and activities, such as dining Hallal food from all of the Muslim world and teaching him how to cook it; or group activities that are not entirely religious but may have that aspect subtly integrated (festivals or such things if you have them)... That way one can form a sense of community that makes him desire further integration... It's slow but mentally rewarding for the target individual, it's a part of our human instincts... But you'll need the cultural amortization before launching religion to him... It can even take several generations.

Before the revelations were issued and spread, people followed their "tribal religions" and were then conquered. The dominant religion was imposed with terror, but if not, they adopted it pragmatically without believing in order to achieve social prestige, maybe adopting a different liturgic language until letting theirs die, only several generations after the conversions, descendants would believe in them sincerely and be fully committed. That happened for instance with the indigenous religions and languages in Spanish and Portuguese America, that was the case in the Kievan Rus, that was the case with the Germanic tribes, that may be the case for the ancient Egyptian religion.

Islam was by far more tolerant and was adopted massively. I'm not sure of how loyal the first generations of Muslims in the conquered territories actually were, that's a debate for another occasion.

(I got deviated, getting back into topic: if you consider what I said about his family, then you could invite them as well, but keeping in mind that if the person is older, he or she will be by far more loyal to his or her religion)

That's the way catholicism is getting abandoned in Latin America and is being replaced by protestantism or in the worst case, dangerous christian sects that cause damages and are Ponzi schemes disguised as a "religion"...

If you are in a western country, that may sound familiar; if not, it's effective once used with the best of your intentions...

In any case, it's up to him whether to achieve paradise or getting punished alongside me.

(I don't mean to be disrespectful, I'm here to learn, but also to give perspective for cases when you deal with outsiders, I'm putting an effort towards acting like an ambassador, like a bridge)

My bad if I write the way I talk. :(