This is all about the right time and place. Find a time when you can walk in on him at a semi-private low pressure setting. When he is relaxed and not under any pressure from a crowd. Despite being all alone with him is not mandatory, some little level of privacy will do the trick. Do not hand out on his porch for hours or behave like a stalker waiting to pounce on the first alone time. You may just be hanging around with a group and then the right moment comes.