As far as the plastic window protection goes - I have been very careful with mine even though I don't worry if they pick up scrub scratches.
Two products have been great - there is a 3M product called Marine Cabin Restorer and Marine Cabin Polish, these two are like a cut and polish for scratches in plastic and perspex that is exposed to harsh conditions. I found that using the restorer will take the edge of big scratches and completely remove small ones, while the polish is good for general protection and cleaning.
Also stuff in a spray called Plexus which is great for protecting and clearing them up if they don't really need scratch attention.
Some dick recently stabbed my driver window with a biro or something
and I have had to mask it with electrical tape. Otherwise my windows have had some pretty full on outdoor and outbush treatment and are crystal clear if a bit gouged.
And I have found that those microfiber miracle cloths actually do work wonders on windscreens just with water - for a streak free finish. I simply wet the cloth and rub down the outside and inside then once they are almost dry buff them with a cotton rag. Really works well - as long as you wash the microfiber cloth first!