I'm using IS Boxer, and you'd likely need to as well to have the same setup.
I'm sure you could accomplish a very similar setup with HKN.

Almost everything specific to my Pally/DK's is in this thread: http://www.dual-boxing.com/threads/3...n-DK-Manifesto

For addons, I use:
- Shadowed Unit Frames, with Player/Party/Target/Target_of_Target and Focus frames.
- My Grid is: Grid + Grid Custom Layouts + Clique.
- I use Chocolate Bar, as my "Broker" bar with plug-ins for Gold, PvP Status, Guild/Friends online, Faction, Experience.
- Jamba is there.
- Mapster is my map addon.
- I use Move Anything, more to hide frames than to move things.
- Overachiever, to see what is required for some titles or rewards or factions.
- My chat is Prat.
- BG tracker is Reflex.
- I have Zygor guides (leveling, Alliance & Horde), but don't use that aside from leveling.

The Paladin has "blank" buttons, on top of the DK's real buttons.
With an icon as close as possible, and a repeater region that goes to the DK's for that same ability.
You can put the keybinds wherever you like really.