The method works as described with the pencils as I have a set myself. I used them for almost a year before getting the Cabine Tree Tester. After getting it I tested everything I had tested with the pencils and came up within a couple of BHN from what the pencils had given me. It wasn't exact but it's close enough to get what I needed to know.
Snuffy has it right, plus usually it is recommended to wait two weeks for the hardness to "mature" or stabilize. That is how I did it as well. I know it is a pain but it is worth it if you want to know about how hard your alloy is getting.
Also the readings you get from ingots will usually not match what you get from bullets. This is one reason I try hard to keep my raw alloy smelting temp within a close degree of what I usually pour at and never over 700 degrees. Usually it is in the mid to high 600's. Then when I pour up the ingots I will also pour up a half dozen or so of the Lee 452-255 RF bullets and toss them in a baggie with my ingots when done. Then later on I can check the actual bullets and know about how hard any future poured ones will be. If I wanted to check the same for water dropped it would be real simple to just drop half of them into a bucket and air cool the others and I would know both ways.
Mike / TX