I work with Alabama Damascus often, and use radio shacks ferric chloride. I like to give a slow deep etch, about half an hour soak then clean/ neutralize. Followed by a light surface polish with 1200 grit paper glued onto a hard flat surface like Micarta. Sometime it takes a second etch to get the desired darkness and always follow up with the light surface polish.
I do agree with most, that properly hardened Damascus etches better than annealed or soft Damascus. Remember absolutely clean steel before etch, finger prints and dirt will contaminate your etching solution and give poor results. Hope this info helps ! I forgot to add as many have mentioned, it is best to dilute your ferric chloride, many folks use distilled water. I use a 50/50 mix of ferric and white vinegar. I also use my solution cold for the long slow soak, a warm solution would definitely speed things up. I have always heard that a slow etch is better than a fast one.
Sincerely,
Clint