MC xxx Request,
MC - go ahead, Or standby (i laugh when i hear the xxx standing by reply)
xxx departed time/location/intentions/ETA
If requiring to submit a plan, can be done via flight watch, or after contacting C with request, give them your departed/location/intentions/eta - then upgrading to IFR and wishing to submit plan. They will then say go ahead with details - give them what they require.
GG