One way to reduce any disparity in your charges is to maintain two or three powder measures. While it is initially expensive, if you've loaded for any length of time, you seem to accumulate them and good quality measures seem to last for a lifetime.

So for most revolver and pistol rounds (up to 12 to 14 grains): An old Redding with a small powder chamber. Even Unique measures well with this set up.

Mid size rifle (up to 35 some grains): An RCBS match rifle measure with a mid size chamber.

Larger rifle (up to magnums) an old Redding with the large rifle drum.

My Dillon loaders have both a pistol measure and a rifle measure to conform to what I'm loading on the press.

Using an appropriate measure you can measure very uniform charges of even the most recalcitrant powders like Unique, Blue Dot, SR 4759, etc.

As noted in the post above, you are probably better off weighing your cases and tossing the heaviest and the lightest ones out if you are shooting a very accurate rifle. While not necessary for standard loads, if you are a long range match shooter, it is more important than a slight variation in your powder charges.

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Keep your powder dry.