It seems to me like it might work to, rather than have most of your members spend a few hours a week volunteering for the Church have all of your members work an extra hour at their jobs in order to hire a professional to attend to those duties.

Cleaning up a beach is one thing, but hiring professional evangelists? I think you'd have a much harder time finding a comparable number of people willing to do it as a job. Plus, how convincing they are matters a lot; a halfhearted manual laborer can get plenty of work done, but a halfhearted evangelist might as well not be bothering at all. How many skilled, committed rhetoricians do you think are available for this particular work for less than the church members are making themselves?