any of the 10xx series of steels will work well for a hamon, generally, the lower the carbon content the wider the habuchi line, ive used 1095,1084 and 1065, with 1065 having the most profound hamon so far. 1084 is a very good first choice in my opinion, with 1095 you have to watch your quench time or the hamon may not be what you expected, and 1065 took me a bit to get dialed in, the hamon tends to be somewhat wider and you have to be careful to get a nice even heat or it may look blotchy. as for clay, ive used straight satanite, furnace cement and a mixture of the two, but i keep coming back to straight satanite for ease of use and quailty of hamon i get, but alot can depend on your quench medium also. ive found with water i like to wash the blade with a thin coat then put it on thicker to design my hamon, however when ive used 1095 with an oil quench the thin wash of satanite didnt work well at all, the hamon tended to dip quite low on the blade, with the 1095 in an oil quench i just put it on thick where i want the line, and have gotten very good results. in my opinion water quenched blades seem to have a brighter and more active hamon, but with water you can have that nasty little PING sound to deal with. also when using atraight satanite be sure it is completley dry, i usually let it set for 24 hours then check to see if i have any hairline cracks in my coating, if there are cracks i use a watery mix of satanite to patch the cracks , put it in the oven at 200 deg for about an hour and then proceed to heat treat. trial and error seems to work well, when you find a system you like take notes and try and get consistant results.