| You can use nitromors if you get the stuff which is meant for glassfibre, Halfords sell this I think, as do paint factors for the motor trade.
Yeti is correct in his diagnosis on returning the shine, smooth it back with progressively finer grades of wet and dry, right up to 1500 - 2000 grade and then polish it as you would paint with a machine. You can do it by hand but it takes ages and will not be as good a finish.
You can polish polyester resin too, which is most likely what you will have.
The other option, as he says is to wet and dry again, but this time only to about 800 grade and then get the parts laquered. This is probably the better option imo, as the laquer gives a measure of uv protection. | 
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