There are a couple tricks to consistent charge throwing with any powder measure. The first is consistency of operation. I always raise the handle (exposing the cavity to the powder) with a distinct (but not hard) knock, then down with a distinct knock, then back away just a hair and give it a second knock. Use the same technique when throwing into the scale pan as you use when throwing into the cartridge cases.
Second, do not allow the powder in the hopper to get too low; I always refill before it gets halfway down.
Third, when first filling the hopper, throw a bunch of charges back into the powder container. This allows the powder in the hopper to settle and achieve the density that it will more or less conistently hold through the charging operation. When first filled, the hopper contents are much less dense than this, and if you set the measure by the first few throws, you will be overcharging later.
Fourth, and this may be controversial, but I always weigh every 20th charge. I have found that sometimes the lock ring on the screw has worked loose and the charge has varied. By weighing every 20th charge, the most I have to dump out and do over is 20 rounds.