I have a rotary electric shaver with 2 heads.
I have found that i can sharpen the blades by taking the head apart and to place the blade assembly FLAT on a 'fine' oil stone.
Then use the motor/drive to turn the blades on the stone for about 30 seconds applying a gentle pressure.
Then wash the blades in warm soapy water and rinse in something like aftershave lotion.
When re-assembled i have found a great difference.
Hope this might help.
Davyd Ford
August 2009