I wanted to try the pencil method just to say that I tried it.
The name brand pencils that were recommended:
Correct me if I'm mistaken, but I gather that the general ideal is to attempt to scratch the bullet with the pencil? If the pencil merely rubs, then the bullet is harder than the pencil. Try the next step harder pencil until you find one that scratches. The softest pencil that produces a scratch rather than a rub is the hardness of the bullet.
At first I tried scratching the filed meplat of my cylindrical slugs. The resulting mark was indistinct -- I couldn't tell whether it was a rub or a scratch. It actually looked like a little of both.
I tried again on the smooth side of the cylinder, instead of the filed meplat, and that worked much better. The smooth as-cast surface provided more contrast than the striated filed surface.
I found it necessary to use a magnifying lamp to discern the scratches. Your eyes may fare better.
Basically my scratch results agreed with the chart below, except my heat treated reclaimed shot did not produce a distinct scratch until 3H.
Like many hardness tests, the pencil test seemed to work better on soft alloys than on hard alloys. On heat treated bullets, there were sometimes several shades of grey between rubbing and scratching. Super precise it is not, but as others have noted it does give ballpark results for not a lot of money.