Pre-weighing works well for me. Next you'll need the little capped vials to carry around those pre-weighed charges. A pretty large number of folks are doing this now. Many contend there is little to gain and that may be so, but doncha just love to tinker?

It's a popular enough notion that MTM picked up on it... http://www.mtmcase-gard.com/products/camping/ml1.html