Rather than pushing a large change agenda, it's often easier to look for "tipping points" of opportunity: where a specific situation exists that can be dramatically improved in ways the people can see---such as going from verbal, unadorned lecture preaching to adding PowerPoint slides.  This can be tried by if the opportunity exists to give a short talk by yourself, to use a projector and PowerPoint slides to demonstrate by-the-doing how this can greatly increase the impact of a talk, with powerful specific images coupled to key words/phrases.  So rather than trying to just make an intellectual case as to how this might improve the effectiveness of using slides, one can connect on an emotional level with the thing itself.

Dan