I've used my EOTech replica reddot for a year now, it works great but one problem, its a bloody mirror. I stand out like a flashlight from the surrounding which isn't great when you want to hide. It's like holding a orange sign "Here I am!". Reddots use a reflective surface, real holographic sights don't. You can see this if you compare the brightness within a real holographic sight and a reddot, the reddot glass is darker whilst the real holographic glass is completely transparent. The other problem is that the surface of the front glass of reddots are convex, so all light is reflected in all directions. This makes you stand out in almost all directions.
The phone is reflecting off the scope, see what I mean?
Killflashes are often the solution, it works great on real scopes but with a mirror surface they don't do much. Sunshades help aswell but not much. The current airsoft killflashes for holographic replicas are rubbish, the ones out there are 3 layers of metal mesh, like the one in mesh goggles. The idea is great but in practice they often become misaligned so you see nothing. That would be if you even saw anything from the beginning and still the mirror shines through, so they see you and you see nothing.
So how do you get rid of this mirror surface? I thought back to my photography days and fishing days. You had polarised glass to remove the sunlight bouncing of water. And there's the solution: polarised glass. You can get this when you watch a 3D movie at the cinema.
Use the reddot front glass as a reference to cut out a piece of the plastic about the size of the front.
Fine tune the edges with a scissor to mount it inside the front frame. Mount by pressing the edges in and with the correct side, the one with which removes the reflection
Tacticool Looks like a real holo except a bit darker. Its a compromise if you don't want to pay 500$ for a real one. You still get some reflection but it's not much compared to before.
As always, do this at your own risk - use some hot glue on a stick to remove it if you need to.
Note: This doesn't protect your reddot at all!! It just reduces the mirror surface. If you want to protect it use plexi/acryllic glass (or metal mesh)