First, drill a 1/4 inch hole in a film cannister. Then cut a piece of aluminum can (about 1/2 inch square) and drill a small pinhole in that. I don't know the diameter of my pinholes - I just made these as small as I could get them using a regular pushpin. I take the plastic top off a 5mm pushpin and load it into a 5mm lead pencil holder to make a tool for drilling a nice round hole. Sand the hole on both sides of the aluminum with emory paper (800 grit sand paper works fine). Tape the drilled piece of aluminum to the inside of the film can with black electrical tape. Align the natural curve of the aluminum with that of the film can and it will fit nicely against the inside of the can.
To make a simple shutter, take another film can without the lid and cut the bottom off. Then cut a narrow strip out of it from top to bottom (about 1/4 inch). Now you have a sleeve-like thing which you can slide onto the camera and rotate to open and close the shutter.
To load the camera: In a dark room, cut a strip of 35mm film and place it in the camera opposite the pinhole. Kodak P3600 works well indoors with exposure times of about 4 sec.