I didn't think it needed lubrication too often...though I found in the manual where they say every 3-6 months and someone else said every 1000 hrs...but I just wanted to have some on hand.
Larry
On my BIII, the manual says you have to remove the pinch roller, the head cover, the right side tape guide next to the pinch roller and finally the "Rear Head Escutcheon" (fancy term for the back cover around the head block)...and then you can finally pull of the Capstan dust cap and place 2-3 drops on the felt collar inside...I guess just to make it wet, but not dripping.