Larry, you don't really 'sprinkle' them on.. I use one of those soft, fan-shaped brushes to 'scoop' some pastel dust then litteraly slap the bristles against the model (mostly the lower parts as I only use pastels, so far anyway, to represent dust).
Once you have slpaaped over a few times, use the same brush to remove the excess, then blow a good time over the model to get rid of whathever is not 'fixed'.
Notice I also 'dust' my bases so that the ground and the model feature the same 'dust'.
From then on, if the model was not already fixed to the base, keep your hands off the model as much as you can.
As to grinding them, just grind the sticks over some coarse sand-paper. Not much is needed.