Your cheapest and probably easiest solution is to use water based paints and I am talking about the hobby type like Humbroldt, Pactra, etc. (go to Walmart, etc. for inexpensive paint), do make sure you use the water based one as these manufacturers also make these paints in an enamel base. You will have to mix a couple or three different colors to come up with the one like on the model, it doesn't have to be perfect. The real birds had lots of repaired and patched up areas and different colors touch ups were the norm, you don't think they had the perfect paint to touch up bullet holes, scrapes, etc. at the field, do you?, besides, paint ages and becomes discolored, and when repairing damaged areas they wouldn't be trying to achieve a uniform look for sure.
Once you come very close to the right color, it is best to mask and paint that entire patch of paint of the same color, the edges are best finished free style, if the areas have a sharp contrast, then it is best to mask and paint within the masked area. Applying weathering helps it all come together and after it is all said and done, then spray a clear coat of satin clear (make sure it is fuelproof) to protect the finish and have that glorious look. I am enclosing a side of my (now defunct) Stuka that I had to repaint and touch up because I had the same problem you did.