Cabrio dipping, how much Dipp???

Moin together… I am here in this forum absolute rookie…. My daughter will soon be 18 and wanted a Punto convertible 176er….Now she came up with the idea you could repaint him….from blue to pink……girls stop… Since I have read so much about dips it seems cheaper and also easier for me… Well my question…has someone ever dipped a convertible, or how much color would you need 2, 3, or 4 liters????