The same upload journal can be used for both Home and Currency transactions using the Currency field in the header.
Where this is blank, or has the home currency code, then this will post to home currency accounts.
Entering a Foreign currency code will allow you to post journals to currency nominals. The exchange rate used to post the home value will be taken from the current default rate set up in the currencies area of system, and may be based on the transaction date if date sensitive rates are in use.