win2K @home, win2K/NT4server @work
No command line to flush. The command line that flushes the client actually starts up a new client that reads the buffers, does whatever fetching/flushing is needed, then exits. This is possible since client buffers reside on disk and are sharable.
Proxy buffers, OTOH reside in memory and are written to disk periodically. So starting a second proxy to do the flushing would do no good. The only way to get the proxy to flush is by sending it a Ctrl+pause (impossible if running as a service). It is possible in linux, but thats beyond my understanding.