The etching solution is freely available called Ferric Chloride - its not nice stuff! But you can buy in quantity from ebay or from Maplin, the stuff will etch brass or copper, think circuit boards!
The trick is not the etching itself which largely takes care of itself once the base material is immersed in the liquid. Nope, the trick is getting your template pin sharp on the substrate, be that copper or brass. There are several ways to do this.
The most popular at the moment seems to be using laser printed paper- the toner can be ironed off the paper and on to your base material, then immersed.
However there is another method I will be trying after the xmas holidays, but until I see the results I will stay quiet about, suffice to say I see an opening in the market for cheaper etched brass than what is available- come on a 25mm brass stanchion costs 72pence, no way!