I alway use molasses sugar which I dry in the oven at a very low heat to stop the rub from clumping.
The quantity I add to the rub depends on the volume I'm making!!!
Surf'n'Smoke BBQ Team
Weber Smokey Mountain Cooker
Weber One-Touch Platinum Kettle - 57cm
Weber Smokey Joe Silver
Film Noir. Back when men were men and broads were dames.