This worked for me.
Wait until the wife/mother/partner/Significant Other goes out. You will need about 30 minutes per flywheel.
Sneak a pair of tights out of the wife's underwear drawer. Make them up into a long, narrow tube about six inches long and open at one end. This is an air filter and should have several layers. Dip into heavy engine oil and allow to drip while you get the engine out into the open air.
Fit a high speed sanding disk into your angle grinder, remembering to fit the rigid back plate first!
Wear a hat, overalls, gloves and - if you have any wit at all - a decent breathing mask. If alone, phone a friend and ask them to call 999 on your behalf unless you ring back within - say - 30 minutes. Switch on your mobile phone, predial 999, lock the keypad and put it into an outside pocket. ;o))
The air filter should be about right by now, so attach it to the inlet pipe and start the engine. Wait until it settles down to a steady rate. You may need to tie the bottom down to stop it bunching.
Apply the spinning sanding disc to the flywheel rim at an oblique angle. grind away until satisfied. To complete the finished work, use a cloth pad to force sixty grit wet and dry onto the flywheel rim whilst it's running.
BE CAREFUL!, spinning flywheels, angle grinders and mains electricity can be dangerous to your continued existence!
Don't forget to phone your friend!