Someone is probably way more qualified to answer the paint question. But for the motorcycle visor option, the hardest part is getting a proper fit in your helmet. They are generally flat and not curved like the in-game models, but if you aren't going for 100% game accuracy (I personally love creative flairs added to suits) this can be the way to go! They are affordable and come with that lovely film that gives the one-way mirror effect you're looking for.
If you are aiming for game accurate, honestly recommend buying one of the printed and painted ones off of some of our friends here in the 405th, through Etsy, or through social media. The nice thing about the ones built by the pros is that they are vacuum shaped (using tools that can be expensive to buy) to match the model of helmet you are building. Most of them are built using flexible plastic and can be installed simply with some hot glue. They also look AMAZING.