I usually mix very finely ground hardwood charcoal with the melted pitch. I don't think I've ever measured it, but I think it's about 25% or so by volume. I collect blobs of hardened pitch off of pines, mostly loblolly just because they're the most common pine around here, and heat the pitch with just enough heat for it to melt. Once the charcoal and pitch are well mixed, I add some little 1/8" to 1/4" "snips" of cordage fiber (dogbane, nettle, etc.)- just to give it some body- plus a few pea-sized bits of rendered deer tallow (serves the same purpose as the beeswax). I store the pitch blend on the ends of little sticks by dipping the stick in the molten pitch, then dipping it in cold water, and repeating until it's built up as much as I want it. To use it, I heat the pitch until it is soft enough to pinch off a ball, then I put the pitch ball in the slot to accommodate the arrowhead and heat it in place until it's very soft, then I push the arrowhead in place. Preheating the arrowhead helps create a stronger bond as well as giving you longer to get it properly in place (something to protect your hands from the heat helps as well). If it hardens up before you've gotten it set in place, the end of the arrow can be held up to a heat source and rotated to re-soften the pitch. I then smooth things up, wrap it with wet sinew and finally coat the sinew with hide glue. I came up with my method by combining information from several sources (Larry Dean Olsen, Scott Silsby, etc.), and it works for me. Keep experimenting until you get a mixture that does what you want it to do.
Will