I admire your dedication bud.
Exactly what I was thinking. On another matter a little tip I have used is when you have finished painting is to rub a piece of newspaper all over the helmet, it adds a nice natural dirty, worn look. That along with black pastal scuff marks helps a lot. You can also highlight/shadow the detail areas with black pastal which makes the helmet look sharper in detail.
I think you have done it anyway but a nice creamy colour as opposed to white works really well if you are going for the 30 year old look.
Keep up the good work.
Joe