Your links don't work for me. Since I have no idea which equipment (tools and press) you are actually using, it's hard for me to suggest a reasonably priced but better alternative.
When using volume tools like the Lee spoons or their auto-disk, its really up to you to find the right volume for that batch of your powder, on that day. You can't fully depend on the info Lee provides as anything more than a starting point. If you are using the auto-disk, they have a micrometer adjustable charging bar that many folks find better than the fixed-size slots.
Once you find the spoon or slot that comes closest to the weight you need, you run into the second problem - consistency. Frankly, *NO* home system that depends on dispensing/measuring volume as a substitute for measuring the actual weight is going to deliver the same charge every time. Many volume measurements are, however, convenient and come close enough, often enough, for a lot of folks.
If volume measurements aren't good enough for you, you'll need to weigh every charge. A well-calibrated beam scale may well be the most accurate tool, but many people feel its the slowest. Many digital scales are relatively inexpensive and are reasonably accurate, with many claiming and often delivering +/- 0.1gr accuracy. You are not likely to get any more accurate than that via any method using realistically priced equipment.
Even good scales leave issues for you to be concerned about. Weights can also vary by humidity, and the scales can be affected by fans, heating/cooling ducts, vibrations, powder spilled on the scale. and even your own breath.
Bottom line, there is no 100%. But there is 99%, and always close enough as to make no significant difference. To help more, please be specific about which measuring tools and press you are using.