A good friend of mine, Darryl Patton, (who is probably as close to an expert on the hand drill that I have ever seen) taught me the technique. Even though it's hell on your hands when you first start out, once you get past the blisters and get good material it's super fast to get a coal. For me it takes a long drill so I don't have to start over at the top with my hands too often. It also takes a fair amount of downward pressure. Funny you mention Yucca. I picked a few pices of the flower stalk going through Arizona one time. Let it dry in my house for a year and I've still not been able to get a coal with a hand drill from it. It seems to get real waxy/soapy when using is on a Paw Paw fire board. Maybe you've answered my question since I didn't let it dry on the plant.
As far as knives go, I haven't found any one maker that the knives consistantly work. The first one I ran across was from Newt Livesay. I also found my Camillus/ Becker Brute works pretty good also. The reason I started researching this is the editor of Tactical Knives magazine asked me to write a story on whether or not the techniques taught in a lot of survival guides actually work when it comes to striking a spak with your knife. As with you, I found that most knives do not work and I found no hatchets or axe heads that will work (not saying there's not one out there that will.)
Anyway, it's good to hear from another practicioner of primitve fire making. As you said, it's almost like magic when you get a fire going with nothing but what's found in the woods.
Oh, btw, my friends call me Jeff, not Mr. Randall.
Jeff