When you came over from the States, you brought along your opaque projector and work table.  The opaque projector allows you to project your photo onto the tortilla.  Your projector is mounted on a projector stand, pointing down at your work table.  This allows you to lay your tortilla flat while you trace the image of the guy's face.

You are using the Artograph Super Prism, which is a fairly expensive projector.  You know they cost around $280 from places like Dick Blick (what a name! you sigh), but you know you can also get them used off eBay.

You know that your Super Prism is overkill for painting onto a tortilla, and just about any projector would work fine.  But you realize that it is way easier to work with a projector that aims downward onto a table, rather than one that points horizontally, at an easel. And the Super Prism is designed for that.