Agreed - if you could put a 'tap' in the bucket, you wouldn't have to break the surface layer that forms from reaction with air.... but for that matter, you could float some styrofoam or a plastic bag on the surface of the 5gal's solution and not have the surface layer either...
I think it all comes back to - whatever you do - will work... just keep in mind that dosing fast can cause pH swings which are hard on your critters.
When you decide that Kalk is the right way for you and your setup - check out some of the other ideas here or in the DIY section and it'll make your life easier.
Best of luck,
John.