You can buy muriatic at the hardware store here, if you can't up there then try to find out where brick masons get their supplies.
O1 doesn't do activity well, it'll give you a line, but usually doesn't get really active. I think Brian is edge quenching, not claying, but I could be wrong about that.
try ferric cholride instead of muriatic , this will darken the steel and get a good contrast between the to area's, muriatic is great for stainless damasteel and that's about it.
you can build a small charcoal forge for peanuts and it will work great for heat treating and for forgeing, this way you can get a nice consistant heat and more control over the end result,
three cinder blocks, a pipe with holes in it and a hair dryer is all you need
you can temper in a toaster oven and you have goodconsistant heattreatment.
Blade finish is also important for a hamon, I handsand to 2000 grit than etch
then clean with semi-chrome
I learned how to do hamons for Wally Hayes video Katana-tac, great info on a basic setup
kinda funny , I learned from his video and now he live around the corner from me . Now I save money on videos
cya
jimi