in summary you will create a seconday copy which will write to the removable drives ( create a library with the MP pointing to windows drive letter assigned to USB disk for example) .Then create a 3rd copy which will do auxcopy from the second copy.
Once th USB drive is available at remote DC ,then share the Mount path to the Media agent in the rmeote DC.
Then enable the UseCache DB setting ( properties on remote media agent and >Additional settings >ADd >Type UsecacheDB =1
Then enab;e DASH copy on COPY3 and select network optimized copy.Run Aux copy for COPY3 with source as COPY2.
once the Job is done then delete the UseCacheDB key.
Copy the job results from Source MA to the REMOTE MA.Then enable signature cache on the source DC
then change the source from copy3 as COPY1.
delete the second (temporay copy) and you are done.
It is well explained in book online