Really? Isn't it easy to wipe out of the embossed areas?
I tried a version of Dr. Chase's recipe but used a dark pigment in stead of lamp black: doesn't work, crumbles out of the embossing. Oil paints should be better to my feeling.
But I now got a powder of a fiend which produces very nice and - he says - waterproof result. He gets it from Italy and it might contain - or just be - asphalt powder (the stuff that is being used in etching so an artist shop might sell it). Needs to be dissolved with turpentine to a paste, so that sounds quite waterproof ! I will test it soon.
I also came across this funny recipe, but I am not sure this will produce good results: http://www.ehow.com/...uing-stain.html