PCB etching in 30 minutes

Here is a very interesting PCB etching guide that is perfect for rapid prototyping.  I like how sparse the material usage is by using a sponge to apply the ferric chloride etchant and home much control you gain.  If my planned PCB milling adventures go nowhere (doesn't start well with the post office loosing my package of PCB engraving bits) this is what I´ll try next.  Heck, I might do it anyway since it's so quick.  Wonder how easy it is to do double sided boards with this technique.