its really pretty cool, and fairly easy
all you have to do is purchase a refractory clay or cement.. satanite is my favorite, and is really easy to apply.. Mix it to a slip like consistancy, and coat it on in the shape that you want the line to show up as.
you can do it as an oil quench too.. just bring it up to critical temp and quench it in the prefered medium for the steel.. I like to use 1080 and 1060 steels mostly, both are fast oil quenches I believe, but I use veggie oil which works fine.
heres what my coat looks like on a simple tanto with a basic wavy line
and heres what it looked like post quench
heres another one too that I made out of mystery alloy railroad steel
I don't know a whole lot of other high-school juniors who are into this stuff though.. so I'm sort of a pioneer in my own right.
I'll post up some pictures