Doesnt mean Im better than you but let me write some advices:
1. Ikhlas doing everything in order to have Allah Azza wa jalla's face.
2. Try to improve your self with your own knowledges in Islam. Cause lets say if oneday he wan to talk to you about Islam, how can you explain it since you dont know anything about it. And more than that maybe he want to compare his religion with yours, so be prepared. And learning about Islam is wajib for every muslim like Rasulullah said "study Islam is wajib on every muslim".
3. Do all sunnah of Rasulullah shalallahu alaihi wasallam. Such as growing your beard, dont do isbal, cause this is syiar of Islam and by doing the sunnah you can lure some qustion from him that giving you a chance to explain ot him more about Islam.
4. Be a good model of how should a muslim attitudes in his own life. Practise Islam. Theres a story about this. Once some of the shuyukh came into the kafereen country and they spent the night in some hotel. And this man, I thought he was a cleaning service or room service always pay attention to what they did. Till one day this man came to the shuyukh and said " I see theres a light on your faces, it seems like ringing a lof of goods. And I see so many kindness in what you do. What are you people? What is your religion??" and then the shuyukh explain about Islam and then this man converted to Islam, subhanallah. Make your self as an example :brother:
5. Try to seek on everything that may interest him to Islam. LIke giving him a present, such as english Quran, or put some Islamic books that maybe interest him in a place that you know he will see the books. Its washilah to hidayah, and to get hidayah we have to do the washilah first. And If maybe you go somewhere with him, then turn on the cassete that talks about Islam, and some others washilah.
6. Bring his family some presents that can make them pleased. If he see you good to his family then he wil feel so happy of you. And maybe he will ask " why you are so kind to my family", and then you can answer " this is what Islam teach me."
7. Keep trying and never gave up. They say "water can make a hole in a rock with a constancy"
8. You may say du'a "wallahu yahdik " means may Allah show you the way.
ok, may Allah make your bussiness easier, amin. :brother: