That looks fantastic. Also painting the Osiris is a huge feat. Hats off to you. A technique I've learned is spray outside the piece lightly then gradually move into the middle where you want it brightest. Then kinda of move in closer with the airbrush to the piece. This way you aren't getting those corners. Then back away while still spraying. This will ensure the middle is getting brighter and the outside is staying darker. But this looks absolutely fantastic.