Although we ran across this fun project on Flickr, you can find Gillian over at Dried Figs and Wooden Spools, along with the full tutorial on this project. To start, she used tape to mask off a rectangle and then applied stick on letters inside. After assuring that they were straight, she used a matte, clear spray paint to cover the area.
The end result looks like an etching process that is subtle and informative, making sure you never open the wrong trash can again. We love the idea and think the process could be used on more items than just trash cans!