Start by setting up a money conduit from the Democrats. Bring in celebrities, fill the March with kids bused in for free food and music, pay some kids to get smartened up to the narrative so they can be the "randomly picked" interviews.
Meanwhile, a lot of unconnected people are going to get $$$ to throw in or just siphon money. A Community Organizer will be able to pick up some paper by turfig the event. Groups like the Communists and Unions will be raising funds for this event. "We need money to help get kids to this March".