Paint with FillBrush I am trying to paint parts of the model with FillBrush, but when I apply the fillbrush it paint all the model

I want to be able to paint of white some part, not the whole model

My model is on a black background and I am trying to paint some parts white

Test:
-If I paint a part green and then I use fillbrush on green, green change to white

-If I paint on the model (texture paint) it paint all the model (from black to white)
-If I paint on the UV map(black background) on a piece, All model is painted

It feels like I am filling 'colours' intead of 'parts'
The Fill Brush does not do what you are expecting it to do.

The fill brush simply fills the entire image, irregardless of color, back facing, occluded faces or anything else. That is true when used in the UV Image Editor or the 3D view.

There is no way with the fill brush to fill just one color, like can be done with in photoshop's paint bucket tool.

The only way you can limit the fill brush's reach is by masking the faces.


In texture paint mode hit Tab, that will bring you to edit mode. 
Select the faces you want to paint.
Press Tab again to go back to texture paint mode. Now press M to turn on the masking feature. (Do note that you can select and unselect faces in texture pain mode when the masking is turned on by  ShiftRMB  on the faces.)
Now when you use the Fill Brush it will only effect the selected faces.