It's quite a thankless task... Here's what I did:

Thoroughly wash the plastics in soapy water.
Dry.
Soak in paraffin.
Wash them again.
Dry.
Plasti-kote primer.
12 hour dry.
Plasti-kote colour (black for me).
12 hour dry.
Another coat of colour.
12 hour dry.
ACF-50 coat

Turned out ok, it has rubbed off in places but mostly intact after 15,000 miles.

I re-did some of it in orange recently.

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Bike: 2013 XT660Z, TKC70 tyres

Mods:
Barkbusters, Scottoiler, DIY Tail Mod, DNA Stage 3, Power Commander V & O2 Eliminator, Exan X-Black Stainless exhaust, Tool tube, Ohlins linear front fork springs, Nitron rear shock, JT front and Supersprox rear sprockets, D.I.D. VX 520 chain, Adventure Spec bashplate, DIY USB Outlet, DIY chain guide, Kev's Throttle mod

http://www.facebook.com/onemooseonemotorbike