Just beautiful! I can't beleive it! Well, I can, but you know what I mean. I love the detail, it really brings this thing up to the next level. Just a fantastic bit of work, here, and I can't wait to see the engine.
For the help you asked for-- silver is hard to brush on smoothly. I think you will just have to bite the bullet and spray it. Use a can if you are still afraid to use an airbrush. People around here use airbrushes like they are going out of style but I for one am still a little nervous about using them.
For the padding (I'm assuming thats what nerf is) on the roll bars, I always used masking tape, and wrapped it around the bars kind of loosely. I often have to run a bead of CA along the final edge to keep it from ever unwrapping. The reason I wrap it sort of loose is because I like to take detail wire (the thinnest I can find) and twist it around the tape real tight, to simulate the zip-ties that hold the foam on, and how it crushes the foam a tiny bit at that spot.
For the front roll cage, trial and error. If you have some measurements and something to mock it up with, great, but you'll still be trying and erroring at the end.
Still, beautiful beautiful. Great work!