Slightly iffy this, but it does work. In my attempts to fit a Parrot handsfree,( finally efficiently fixed by nice man from Norwich In Car Entertainment for £40,) I put a gouge and many small scratches in the coloured pastic part of the dash. To remove them I used a Bosch electric paint stripper gun on a low heat setting and gently warmed the dash area until they disappeared - as if by magic. The gouge is just visible but smoothed over. Please be very careful if you do this, I accept no responsibility for molten pride and joy. ( I did have a fairly good idea this would work - we make industrial packaging machinery and do this all the time to refurbish scratched see- through panels)
Yes I have heard a hot air gun works well on plastic scratches, especially on those black embossed plastic door trims which scratch when you scuff them with shoes getting out the car. Needs care though, and I haven't been brave enough to try it!!
Very clever ... but you obviously are a bit of an expert.
I am guessing it works well on solid colours especially white.
Not something I'd recommend for the rest of us ... I can just picture scorched dashboards!!