Another trick if you don't have the cash for, or care to buy a set of weights is to make up some tin-foil balls and "calibrate" them on a known-to-be-correct scale, put them in a little zip-lock bag and label the bag with the weight using a magic marker.
If you want to get really slick, buy a few different colored Sharpie fine point permanent markers, color each foil ball check weight a different color and write that weight on the bag in that same color. Now you can put them all in the same bag for simplicity.
Sharpie pens also work great for sealing primers and color-coding loads all at once. After drawing around the primer of a loaded round, put a mark in that same color on the label of the box. Now it's easy to tell where the load came from should it become separated from the rest, plus the sealed primer as an added bonus.
It all works just fine for me
SM