Painting Question

I'm practicing on painting a car (using GIMP), and I used bucket fill on the deck lid and it didn't completely fill the deck lid, what am I supposed to do?

Okay:

What type of car is it?

I'm assuming it's either a Dash Cup or Default Cup, if this is the case then:

Use the free form select tool (looks like a lasso) and click a path around the trunk (deck lid), create a new layer over the base color layer and fill the selection in, it doesn't matter if you extend the selection to the rear of the document as long as it doesn't not overlap the rear spoiler.

There should be body lines that show where the deck lid is, use the ffs tool to follow those and do the above.