The best way to bring out Hamon is use small fingerstones that are very alkaline . They actually etch the blade steel, without removing too much material . A hamon or part of hardened edge is merely a surface feature that can be
sanded out . The less the steel is alloyed the better the hamon. The previous poster is correct Hamon does not like heat . Too much much heat will destroy hamon . As little as 300 F will make it toast.
The Japanese who pretty much invented it , don't use long tempers , it is all done by flash temper . bring blade up to 300 f and that's it! Pic of hamon that was flash tempered once .Counter polish is another way to bring out Hamon.