I would reccommend rub 'n' buff, if you know how to use it. I would reccommend something along the lines of priming the part you want to shine, then wet-sanding it with 600, then 800 grit sandpaper. For wet sanding, it tells you everything to do on the package of the sandpaper if it is the waterproof sandpaper. Then after you got it all nice and smooth, apply the rub n buff with the palm of your hand and buff really hard and fast until you feel it heating up, and when it gets hot enough it will sort of seal and you should feel the difference, but you have to get it nice and hot. This also does not require a lot of rub n buff, just spread it evenly. I hope this helps you out!
(Don't look at my armor for my costume and expect to see results of this meathod, because I found out about it after I had done nearly all the peices with 220 grit sandpaper.)