Thanks, folks!
Mike--I did the panel lines with a standard sludge wash made with Polly S grimy black and dish soap. I found the recipe for it in an old FSM article.
Russell--yes, this aircraft was from the 65th Squadron, 57th Fighter Group in Italy in 1944, according to Hasegawa's instructions.
For the weathering, I tried out a new technique used on armor models fairly often--the dot painting method. I dabbed on small dots of oil paint over the flat coat and brushed them down until they were almost gone. On the OD surfaces, I used white, yellow, blue, and brown oil paints (concentrating the lighter colors on top surfaces), while on the bottom I used blue, Payne's gray, white, and brown. This build was a fun learning experience overall. For my next aircraft project, I'm thinking of tackling a NMF F-86. I hope I won't be biting off more than I can chew with that one!