hey Al, sorry for not getting back to you sooner. Let's take a look at part of your Stang and see if I can get you a little closer.
I opened your stang and duplicated the base layer (lineart) highlighted pinkish.
on the duplicated layer I zoomed in on the corner and used a small brush and painted a little connection line so I could close that fender shape. Yes I could have selected the area another way with the polygonal lasso or something but I chose to go this route with this. There's a thousand ways to do everything in PS.
This layer is your selection layer. It won't be around when you're all done.
Then I made a new layer. Layer 2
I used the magic wand and clicked in the shape not the outline on my selection layer. Then I click to make my new layer active and I filled the shape here. The selection isn't layer specific. I can select on layer 1 but fill that selection on layer 2. Oh! I expanded my selection by 1 pixel. You do this so your fill will be trapped by the black line eventually. You can expand a selection byt going to selection-modify-expand. (That's kinda important. You don't want white spaces).
I moved your initial lineart layer to the top of the layer pallet. As you can see it's all black and white again.
When I set that lineart layers property to multiply all the white drops out and the black is merged with whatever is under it which makes a great black trap line.
If you want the lines to be colored only create a new layer above your lineart layer. Fill it all with a color and set the layer property to color.
Once again this is just one of a thousand ways. I only know what works for me. Any suggestions from all of you are goods ones. Join in.
-Lemorris