Hey Jay Jay,
I used my own mix of Tamiya paints for both P-40's.
On the P-40N, for the faded OD, I used XF-67 Nato Green mixed with XF-57 Buff. (XF67:2 + XF57:1 thinned 1 part thinner for each 3 drops of paint) The bottom is straight XF-53 Neutral Grey. All of these are thinned with 91% Isopropyl alcohol. Before and after decals, I used Testors Laquor gloss. After the 2nd gloss coat, I sprayed a highly thinned mist fo XF-57 (about 10% paint, 90% thinner) to fade the OD even more. After another gloss coat, I used the Dark Dirt Flory wash over the entire model to highlight the panel lines plus add dirt/grime to the rest of the paint.
On the P-40B, I used the same mix for the faded OD, and for the Tan/Earth color, I used XF57 Buff mixed with XF-52 Flat Earth (XF57:2 + XF52:1) thinned again with 91%. I didn't use a mist of XF-57 on this one but did use the Flory wash.
Steve