I've just reprinted the front bumper skirt of my project car using colour matched rattle cans from Halfords. The colour match is really good but the finish isn't. It's like gun finish but really heavy. Firstly, how long should I leave the fresh paint before polishing it smooth, and second, should I go straight for the Farecla G3 or sand it first, and with what grade paper? 1200 or finer?

Give it a few days to harden up, then I would be using 2000 grade, with a few drops of fairy liquid in the bucket of water. Take it very gently. Then probably something a bit finer than GŁ, T cut may be more suitable. You dont want to rub through.

This is the bumper as painted


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and here is a close up showing the gun finish


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Although I have never done it to a finish coat that is almost worth spraying on a very light mist/guide coat of say white, and using it as a sanding guide with for wet n dry. Sand till the guide coat is gone. Then polish.

Go extremely careful on those edges when colour sanding as less paint gets on the edges so be careful not to sand through to the primer