Doing a rubbing does not require much in the way of technical expertise or artistic talent.
Here's a Quick How To:
1) Take a sheet of regular drawing paper, tracing paper, or mylar (any paper that will allow the texture of a surface below it to come through will do);
2) Hold it up to the wall/surface so that it doesn't move; securing the paper with non-sticky tape is easier, but, not every synagogue will allow you to do this;
3) Take a crayon, or pencil-stick, or some form of dry color stick and move it back-and-forth across the paper until an image forms from the texture that is underneath (hint: rip off the wrapper on that crayon; use the broad side!);
4) Make sure not to leave any marks on the surface of the wall, doorknob, etc. Never deface the surface in any way! This should probably be point number one. Always keep it in mind.
5) Make note of the date on the back in English and Hebrew time, and the location. For instance: 7th July, 2008; Av 6, 5768, Synagogue Shaaray Tefila, New York City
Things you Might Want to Know:
Lots of synagogues have high security these days. If I see a security camera, or a guard, I go inside and ask first for permission to rub. This is often an interesting (and meaningful) escapade, in and of itself. Oftentimes I go at off hours, and no one is around, so I just make the rubbing as respectfully as I can (you want to put passersby at ease, too)—and leave. That's interesting, as an event, as well. How you encounter the site—the weather, if anyone's around, people you might need to meet—is all part of the experience. Sometimes just having a brief conversation with a stranger at the temple is enough to begin a deeper 'conversation' about this period of time. Consider keeping a diary or making a map of your itinerary.
What would it be like for someone in Virginia, in Prague, in Berlin, to do 8 rubbings in 9 days? Would it require overnight stays? How far would they have to go to find a shul? Rubbings are the best record in my opinion for this project, but photographs, also, would be cool. Feel free to take them and send them to me.