Try Prima Slick - I used it for the first time today and bugs literally slide off the visor! I also used on the plastic fairings on my S4RS and it hid all of the fine scratches. It works much better than the Honda spray or Plexus...Ive used both.
I just wait till I get gas then walk up to the squeegee dispenser, a couple up and down motions, a swipe of the paper towel and I'm good to go...
I usually just clean the helmets visor with windex before I take off on a ride. If the bug layer is more than a 1/4" thick I'll scrape some of them off with a plastic putty knife so they don't obstruct my vents and interfere with my Arai built-in AC unit. Sometimes I leave the bigger bugs on there to scare away the other ones.
I hate mirrored shields...I think they look cool but they don't last. Had bought some silver ones in the past and it all smeared off with WATER. These were ARAI shields that were 80 bucks a pop! Took them back in one after the other for replacement and the dealer did, but it must have been a bad batch or something. I have about a dozen clear and smoked shields all sitting in my riding closet so I can easily change them out. Some dark smoke and regular smoke and that's about it. Of course, being a painter I've got about 20 helmets laying around so that's why I've got so many visors...lol
I like Meguiars stuff to I use their plasitc polish and scratch remover. It won't work on iridium or mirror finish shields but it will take the scratches out of the smoke and clear shields! Works great! My Suomy shield is a mirrored finish so I just put a hot,wet paper towel over it to loosen the bug guts and stuff, then wipe it w/ kleenex or a micro towel. The Meguiars stuff also removes scratches from DVD's too!
If you got bugs that are on it that have hardened, the best thing you can do (and really the only thing I do)...
Is get a large paper towel, soak it in water and cover the visor, pressing onto it to get rid of the air bubbles. Let it sit for 10-15 minutes. After that, *slowly* wipe the towel away, flip to the clean side, and slowly/softly wipe down the remaining bug crap off the visor. Then I dry with a dry paper towel (again, use a soft touch).
The wet paper towel hydrates the dried, scratchy hard bugs so that they come off easy. Otherwise, you have to push really hard and essentially scratch the crap out of your visors trying to wipe off these rocks that are stuck on. At no time do you ever want to be pushing hard on the visor, because that is asking to scratch it up.