Damn you dirt!!!! The way the lower cowling looks I'm wondering if it is a 2 color scheme and they used stippling to blend down to the white.
It definitely does look like that. I'm wondering if a dark navy blue for a layer, then a very light brown to give it that 'blue-jeans' look?
Bottom - it does look like stippling underneath - especially the cowling.
Here's another dusty F4U + sunbleached
Pretty good color image of the F4U (carrier - clean)