personally mate i would take the handles off or get a set of spares from a scrappy or ebay. i would then put the handles in a bucket of water and sand them down under water with 180, then 240,then 320, then 400. make sure the handles are kept under water when you do this. the idea of this is to loose the texture in the plastic and take that horrible grain out.
it will not be a quick process.
when this has been achieved degrease the handles to ensure there is no silicone still on them as this will cause reaction.
i would then use plastic primer and give the handles a nice clean coat. when the handles are dry i would get some 800 wet and dry paper and rub these down very gently until you can see no imperfections in the primer.
the next stage is to paint the base colour, i would reccomend going to a good paint supplier and getting the exact colour matched up in a tin so there is no need for a compressor.
paint the base coat on but dont go to heavy. when you have done this let it dry. a good trick here is to get some 2500 grit wet and dry paper and rub the base coat down so it turns a matt colour. this will also remove the dirt if any has got into the base.
the next stage is to lacquer the handles, this is where most people go wrong and the lacquer goes all horrible and runs. firstly do a gentle dust coat so it looks speckly , let this flash for a few mins. this will help the good coat of lacquer adhere nicley and shouldnt get any runs.
next give the handles a good coat of lacquer but dont put too much on because it will run. the idea here is to get a good "wet look coat" so that it looks normal.
once this has dried you should all being well have a good quality colour coded handle
refit and enjoy ! if you need any more advice then pm me !