Despite all the dramas, the finecast changeling has painted up nicely in the end.
The undercoat for the miniature was done with dheneb stone. This was followed by multiple washes of various mud browns to darken the tone in the recesses and raised with bleached bone highlights around the edges of the billowing robe. I attended to the arms next with a basecoat of ultramarine blue. They were inked (old-school ink) in blue, then highlighted with a combination of ultramarine blue and electric blue.
With those two main areas painted, I moved on to the finer details, including the flames (basecoated white, twice; followed by successive layers of yellow, orange, red and dark red in sequence), the staff (basecoated in bleached bone, several washes of devlan mud, highlighted in a mix of skull white plus bleached bone, followed by some triple-zero paint brush work to squiggle some letters on to the paper), and other ornaments (golden Tzeentch symbol, armbands, the rod of the staff).
Overall, I'm happy how this has turned out. But I will avoid purchasing finecast if I can help it, despite GW staff being very helpful in their exhange policy.