Mine would be:
Make sure that you mix your groundbait for the feeder quite dry, I only use a spray bottle for feeder mixes.
The last thing you want is a wet mix that refuses to "explode" out of the feeder. Riddle it well, 2 or 3 times in fact to ensure a lot of air is present.
If you are using a powder additive then mix it in (dry) at the riddle stage.
Adding to Beecy's point - not only will the hemp dry out in the groundbait, but it will also over-wet the mix if added all at once.
If at all unsure about the consistency then simply drop a loaded feeder in the margins and watch the result.
If too wet, add more dry groundbait, mix really well, and then riddle it all over again.
Also, on those warmer or windier days I always use a damp (and I mean damp, not soaking wet) tea towell laid over my groundbait tray to avoid drying-out of the mix.