Air-Valve Autobot!
I'm planning a project which is a B&W image , the object is white and the background is half white half black fading in the middle , so I evaluate to paint it over a black canvas , So I can use white to make corrections without worries about white blue shift
I make some practice , by soft layers to build the shadows and highlights , but when i reach the third layer , I can't get rid of the "ghosty" look , which is good for skulls and to put candys over , but here I search more realism.

My chances are

1- paint it on white canvas as usually
2- Paint first a strong white base in the black canvas and paint as if was white
3- keep adding more and more layers till its done

What you recommend ?
It would help me more if you had some kind of a reference picture to show what effect you are looking for.
As I understand it you are doing a fade to black piece. starting with a black canvas.
Me I would build my whites slowly using up to 5 to 8 layers until I got to my brightest white.
If you looking for more of a hard edge look use a shield on you fist mist coat to get the edge you are looking for.
That is if I am understanding what you are trying to do.
I have to say go with the white canvas on this one being it will be easier to catch the shadows and the out line if the slippers