Hi Rob,
My main advise is NOT to get too worked on it. At the end of the day, IMO there isn't much to it. Just use common sense.
My main tips are:
1. Spray with water using one of those misting bottles to remove as much dust/grime as possible.
2. wipe over gently (no heavy pressure) with cotton wool strips dipped in water and detergent (only need a few drops of detergent into a bucket of water).
3. Use a spray bottle to remove the suds.
4. final rinse with distilled or de-mineralised water.
The mirror should be tilted during the cleaning process.
And the most important tip. Don't attempt to dry or remove any droplets using the cotton balls/strips. Let it air dry.
Good luck.
Norm
PS: something better than cotton balls/strips is these things called:
'Swisspers' woman use them to remove make-up and can be purchased at supermarkets or chemists for a a couple of bucks. They're flat shaped and larger than 6cm in diameter and come in packs of 80 - perfect for mirror cleaning - specifically cause they don't leave any fine lint or cotton hairs.
(they are 100% cotton too and you'll only end up using maybe 2/3).