Hi Mustang,
The dreaded seam filling and sanding, it's my least favorite part of model building, especially with raised panel lines on Revell kits, so I don't envy you :(
I picked up some AK 3rd generation AK11023, FS34031 last night to compare it to my color chips and it is a very dark forest green, it's close to FS34031, but I need to test how it scale fades and modulates to the theatre of operation still. None of our Apaches or Cobras looked too pretty in the hot Texas sun vs. cooler climates like in South Korea so it's kind of a challenge how much pre and post shading and color modulation you can get out of your base color.
You mentioned you are using Vallejo Olive Brown, if that is item no. 70.889, or FS 34084? Just be careful it might turn too brown if you scale fade or modulate the paint. Vallejo 70.980, 70.896, 70.897, or 70.70.979 may stay more to the FS34031 green side than brown. But I find experimenting is half the fun in painting.
I switched to acrylic lacquers because they spray better with no tip dry and I find it easier to weather and modulate sun bleaching with oil pin washes on a gloss coat after decals. However you can still do the same with water based acrylics though, just slightly different techniques.