I don't remember a brass flywheel i there but it doesn't matter.
The mirror squeak has no effect on shutter speeds either. the shutter is released when the mirror reaches the top of it's travel & hits the shutter release lever.
Anyway, remove the lens. There are four screws visible on the front plate, remove them and lift the plate straight off.
The lens mounting ring has four screws holding it on. Remove the TOP LEFT screw. The mirror governor is just under this hole. with your oiler 2-3mm into the hole and angled away from the mirror box apply a drop of oil. Work the shutter several times and as the oil flows downward it will lube the shafts. Put all the screws back & you're good to go.