I use the standard 1 part HCL to 2 parts H2O2. I place the board face up in a shallow glass or plastic container and mix up enough etchant to submerse the board in about 1/4 inch of solution. The etchant is at room temperature. I gently brush the board with a cheap foam paint brush until it's etched. Takes about a minute or so.
You can see the results in the "Photos" section titled "
Dissolvo Paper Experiment"