Always remember to invite the Holy Spirit in whatever you do or say and that its only God that can change people, not us. We can only show them the way, but God is the one that brings them to change. God bless
Your friend will of course have to make up his own mind of course but this I know; prayer can move a mountain.
Be led of the Holy Spirit and like esthy09 has said ask the Holy Spirit to be a part of what you are doing here. In my experience I have never met a person who (if I talk to them in a quite moment) is not willing to pray with me.
Empathizing with their struggles (genuinely) and listening to their problems is a good way to bring up the subject. Sometimes a simple would you like to pray and seek God about your issues will open a door that will bear much fruit.
I will be praying for you and Billy my friend.
Many blessings in Jesus wonderful Name,
your brother Larry.
Dear Father I pray for pressure that U give him wisdom that he knows is from U, I pray that your spirit would move upon him in a real way that he knows it full well that the knows it is you. I pray that Billie would hear your message father and respond to the reality of knowing you through a personal relationship through your son Jesus. That she would see that there is no hope because of her sins without you son. I pray that Pressure would not pressure on a decision but show her that she needs Christ because of the sin and its eternal consequences of not knowing Christ as her sin bearer. in Jesus name do I pray.