I have used the beads (Equal) in my first set of replacements tires, and this most resent set. I was satisfied with the results, but did have problems with the first set getting small debris in the valve stem, resulting in a leaky valve stem. It looked to me like the first set was a powder like substance and the second set were more like glass beads. This last set also, came with it own set of valve stems that appear to have a screen around the base of the stem.
Anyway, I heard that the powder material can ball up and become hard over time and with the use of moist air in the supply line. Truckers seem to be happy with 3 golf balls in the dual tire and 4 balls in the single (maybe the other way around). Sounds crazy, but I have heard that from a number of truck driver/owners.