In theory we all could present the gospel message to all that pass by us in the same manner that street preachers do.It's important to realize that even most of those who have received the Holy Spirit from God do not have the gift of preaching or prophecy as this gift is identified in the verses below,but rather have been given one of the other gifts the Holy Spirit grants.
1 Corinthians 12:8-11 (Contemporary English Version)
8 Some of us can speak with wisdom, while others can speak with knowledge, but these gifts come from the same Spirit. 9To others the Spirit has given great faith or the power to heal the sick 10 or the power to work mighty miracles. Some of us are prophets, and some of us recognize when God's Spirit is present. Others can speak different kinds of languages, and still others can tell what these languages mean. 11 But it is the Spirit who does all this and decides which gifts to give to each of us.
There is no such thing as a Holy Spirit gift of witnessing which no doubt explains why many find it difficult to engage in this practice especially if they are burdened with even a slight trace of shyness or a heavy dose of modesty.Most significantly,all of the gifts the Holy Spirit gives to Christians,including and especially the gifts of knowledge and wisdom, are to be used in a very personal manner to give guidance to individuals whom God has personally chosen and not to masses of individuals and certainly not to random strangers rushing by in their mad mercenary Xmas shopping at Walmart, even as much as they certainly need it!