Nice job on the helmet it looks great and so does the rest of the armor you've completed so far, also if you really want to mold your helmet the silicone shouldn't harm your paintjob, keep up the great job
Interesting, thanks. I'll look into it, maybe I will try it then. When I have time of course!
As for weathering. For most of the armor, after I had all the colors on, I took a plastic bowel and sprayed silver spray paint into it. Then I dipped a chip brush (a really cheap disposable brush) into the paint and brush the silver on to the corners. The brush leaves scratch-like marks on the armor. After that, I use an airbrush. I use black on raised edges to give general wear. Next comes brow. I hit all the corners with brown, because that's where dirt would build up. Plus, I give most of the model a light spray, and sometimes I mix up darker browns for more color.
The brown and black can be done with washes, which are watered down acrylics. I've seen a really amazing painting video somewhere on here before. Though I don't know where to find it.
If that's not very clear, I can make a video next time I paint.