So basically remove it from car, paint and leave it cure for a couple of weeks is the best way?
Spot on.
That makes no sense at all

I'm guessing that the damage was done over a period of time last winter, with roads being gritted and salted to the hilt, and pothole debris being thrown at the valence in question...
Cure, strip it back to plastic, have a paintshop apply the correct primer for the plastic, the 2/3 coats of high build primer, with a plasticizer flexiable additive added, then colour (some systems don't need a flexible additive in the colour) again with plasticizer added, then 2coats of Lacquer, again with flexible additive mixed in, this is about the best chance that you have using any paint system, but trust me, it wont last, 2 weeks to dry, or not!
If it were me, I'd get it painted, and cover it with "Helicopter Tape" job done, and almost invisible, and when it gets tatty, just peel it off, and re do it
http://www.tridentracing.co.uk/info/various.htmThom