Volks, my brake lights are not lighting up properly.  To light them requires pushing on the brake pedal very hard, harder than required to stop.  Cleaned taillight housing contacts and contacts on master cylinder switches with no change.  Could the switches at the master cylinder be bad or clogged?  How much fluid will drain out if I quickly swap out the switches at the master cylinder or better to suck out the fluid from the reservoir first?  
TIA

Jeff