The GWP evangelist has two daily tasks to be done before the public: preaching the Gospel and asking people to participate.
The GWP guidelines say that evangelists are to preach the Gospel for four hours daily. In preaching the evangelist of course asks for responses to his message(s). The hearers response leads the evangelist to be able to minister to them and allows for continual interaction that leads the evangelist to continue to ask for the hearer to respond.
The evangelist also has the responsibility and opportunity to invite people to partner in their ministry. In similar fashion to preaching the Gospel the evangelist explains their ministry to people and asks them to partner by evangelizing with him, praying for the ministry or giving financially.
In both scenarios the evangelist simply preaches their message and asks for a response with the hopes that the hearer will respond in faith.
Thus if you can or learn to preach and ask you can be a full-time evangelist.