It's pretty easy, and they look good actually.
You must copy some of the contets of AnimationSystem3p.inc inside the soldiers_server.zip/british_male_soldier to the one in soldiers_server.zip/german_male_soldier (or vice versa). To make the airplane emote availible for a National for example you must copy these parts
animationSystem.createTrigger Trigger airplane
Look up the original code to figure out where exactly.
Copy the .wav files. National ones are in sounds_client.zip/VO/Russian/West/Emotes, Royal in sounds_client.zip/VO/English/West/Emotes. Copy them so all the National and all the Royal emote sounds are in both those folders
Add the Itemids of the emotes to the defaultcustomization.xml (if you haven't already) to get them in your equipment.