About a month ago I wrote about the five options for people who want to come to the U.S. as a m-ssionary using the B-1 visa:  Those are:

• Ministers of Religion coming on an Evangelical tour in the United States. This is for people like Billy Graham — but of course, you don’t need to be famous like him.   You can go around speaking at churches or at any venue.  I doubt that it has to be what is traditionally viewed as evangelism — it could also be, I think, someone who is sharing his vision or a word from God that he believes people in US churches need to hear.  I think this would also qualify for missionaries who come to the US to share about their vision and to call people to participate.   It is not for raising support, but, for example, a Presbyterian could share about his ministry, and people could be moved to contribute to the Presbyterian mission agency, which could then use that money to support him.   It is possible that you need to be ordained to do this.
• Ministers of religion temporarily exchanging pulpits with U.S. counterparts. This is mostly just a straight exchange where the foreign minister is just coming to serve in that specific church temporarily (probably for a very short period).
• General M-ssionary Service. This is for anyone, whether “ordained” or not, entering the United States temporarily for the sole purpose of performing m-ssionary work.   As stated earlier, “m-ssionary work” for this purpose may include religious instruction, aid to the elderly or needy, proselytizing, etc. It can be quite diverse in what you are doing, and will cover most of what people come to the US to do when they are seeking to serve G-d here in the U.S.   However, it does not include ordinary administrative work, nor should it be used as a substitute for ordinary labor for hire.   But even here, if the person is engaging in the administrative work or labor is a way of serving and advancing God’s kingdom, there may be ways that it can work as well.
• An applicant coming to perform voluntary services for a religious organization, and does not qualify for R status. This is similar to the previous scenario, but it emphasizes service to a religious organization rather than coming to serve on your own.
• Aliens participating in a voluntary service program benefiting U.S. local communities, who establish that they are members of, and have a commitment to, a particular recognized religious or nonprofit charitable organization. This is broader than the prior categories in that it includes nonprofits which are not specifically religious.   But, otherwise, it is very similar in the breadth of the ways in which people are allowed to serve.