I keep mine in an old Plastic Waste Paper basket. It catches any of the mess.
The secret is the pull back the spring and activate the lock to take all the pressure off the Grease in the cartridge.
Without the pressure, there is no reason for it to leak.
My thought as well. You should never need to be adding grease just before launching.
I put a couple of pumps into my bearing buddies when I get to the launch site.
Knock it offYour hub seals will thank you.
If you need to add grease every time you launch, that grease is going somewhere, likely out your rear seals. I have bearing buddys and never have to add grease once they are full.
How long can this subject be discussed?.....