Do you have an hour? I'll call you on the phone and we can get a good start at explaining the need for repentance. Sound good?
The Gospel can be presented in about a minute or two. Why do you need an hour? Don't you think the Holy Spirit can convict someone of their sin and their need for repentance without an hour long lecture from you? People recognize that they are sinners. The problem is most people don't care. If they don't care, then they won't repent. If the Holy Spirit convicts them of their sin, then they are open to repentance.
So, I'm a sinner. I know it. I don't like it. It makes me feel bad. What do I do now?
BTW if the Great commission is to apologize for Calvinism, then "I'm sorry" for Calvinism. :-)