Looks good. A couple suggestions for ya.
1: I can see on the cheeks the different masking lines where each piece of masking tape was placed to define the curve.
Heres a trick you might try.
At walmart in the Craft/Fabrics section. They have 1/8th Inch Quilters Masking tape. Get you a roll of that. Its about $1.50 I think. But then when you go paint the curves right there, take the masking tape and connect it to one side on the bottom, then hold the bucket in your lap, and you can use your finger while pressing the tape down to curve the tape to the helmet. This will give you a nice solid line when you paint. Just make sure that you do add the rest of the masking tape over it to cover the rest of the area up before you paint.
2: for the silver weathering. This is an idea adopted by our resident painter pro's here. Its the "Mustard method". After you have the silver base...I take a pencil...and draw on the damage. That way you can match it up with the Movie Armor as accurate as you would like. Then get a fine paintbrush...dunk it in some Heinz Yellow mustard, and start covering it up. Then paint over that.
Its looking REAL good so far man. Look on here when ever you got questions. There is so MUCH vital information on these boards that whenever you get in a bind, just search it on here.
Specially anything from Rogue Studios...that guy is the MAN. So keep it up bro. Its looking great.