Go through the Knowing God Personally Booklet
Read the Gospel of John (together and on their own)
Read Tim Keller’s Reason for God and discuss it (in its entirety or more practically read the chapters that are relevant to the specific questions and barriers they have)
Take a new believer through these follow-up materials (if possible print these double-sided flip on short edge and it makes a nice pamphlet)
”What you have heard from me in the presence of many witnesses entrust to faithful men who will be able to teach others also. - Apostle Paul