yeh you would need to import the model in blender or whichever software you choose
if you want "perfect" skins its really the only way............and i am talking 100% perfect
the amount of time's i have said "i wish i could uv map" is in the hundred's, i just dont have what it takes to do 3d let alone the computer for it.
so i go by the "it is what it is" quote
if i do a car and its that bad i just dont do it and find another car instead
although you may be lucky i think someone has pointed out that those bits are hidden in the ao on that car
my advice for that would be to make the AO layer slightly transparent so you can see more........sometimes stuff is hidden in the AO this has happened to me on alot of the stuff i have done, best practice to always mnake that layer slightly treansparent as one of the first things you do
also when you have a car that you dont know, just chuck a few random shapes e.t.c all over it..............just to see what its mapped like.........the last thing you want is to get 50% of the way through the skin only to realise the uv is unusable in certain area's and you then realise you wasted 5-10-15 hours....i hate it when that happens and its always when your trying to do something REALLY accurate.........