Vinegaroon is not a dye, it's actually a chemical reaction with the leather so it's not really something that is going to work well with just trying to get the top layer colored. And it should take close to a month for a batch of vinegaroon to really work well. And as Red Cent says, dunk it, wait only a few minutes then put it in the baking soda solution. If you let it sit for a day and it barely touched the surface, your vinegaroon wasn't ready to use. Vinegaroon shouldn't have much of a vinegar smell once it's ready to use.