Bruno, I'm currently using exp/imp with fromuser/touser as Simon said
above. E.g.:
$ exp myprod/password consistent=Y owner=myprod file=/tmp/myprod.dmp
$ imp mydev/password rows=y show=n ignore=n fromuser=myprod touser=mydev file=/tmp/myprod.dmp
That will definitely work for what you want to do too. But, it was
the slowness of the import step that led me to start this thread...