You should be careful if you use aerosols on helmets as some of the solvents in them can weaken the plastic of the visor.  Washing up liquid contains salt that over time can scratch visors

If I am out and about, then a V2 sponge works a treat.  At home, then the kitchen roll soaked and placed on the visor works a treat.

Microfibre cloths will polish the visor.

A V2 sponge wrecked my visor. I followed the instructions about wetting it and putting it back in the bag, then the first time I used it the anti-scratch coating went all foggy. Unfortunately it was boxing day and I was in Snowdonia, so getting a replacement was out of the question, and I had to ride home without a visor. I'm sure plenty of people are happy with them, but mention it in my presence and you'll get cursing. 
                                                                                                                                                                             

Curse in front of me and I will slap your wrists young man 

Don't fancy riding visor-less at that time of year.  Not for that distance, did your eyeballs freeze?
                                                                                                                                                                             

Thanks for bumping this.    I forgot to clean it after Barmouth and I need it again this weekend                                                                                                                                                                               

By the time I got home my eyes were bloodshot and very sore. It wasn't just the cold, the roads had been gritted so I was bombarded with salty spray too.Thinking about it now, I was trying to clean spray off the visor so the salt might have been part of the problem