Flew RAF VC10s and also the Oman RF one too, totaling about 3,000 hrs on the type and NEVER ever used reverse thrust in the air. If speed were reduced below the gear limit, (my fading memory recalls this being 254 kts) one could always lower the gear and with flap the aircraft would go down like a lift.
Even when the speedbrakes (spoilers) were deployed normally there was a degree of airframe vibration which occurred and I would suspect that accounted for the vibration referred to by the instigator of this thread. Until about the mid 1980s it was common for the operating pilot doing a pa to the pax at 'top of drop' and mention that if a quickish descent were required because they had been held high by ATC, then the speedbrakes would be deployed and that they would experience this vibration which was completely normal and nothing to worry about. In time this mention on the pa was skipped as many of the pax were 'frequent flyers' and knew about it