Not sure about 1/35 skin-tones, on larger Kits I have used a few formulas successfully:
1.) David Fisher:
Ratio of 1:3:6 using burnt sienna, raw sienna and titanium white this basic forumula will give you a generic caucasian colour using paints like liquitex and similar.
2.) Anime flesh (can be darkened for caucasian flesh):
Ratio of 8:1:1: using yellow orange (#58) and red(#3) and sky blue(#34) and Mr. Base white from the Gunze range.
3.) Another colour mix I use at times:
Character Flesh 1 + Character flesh 2 with hints of clear blue and clear orange also Gunze range.
Neither of the above are oils, but are all acyrlics or enamels.
This will give you a base colour (prepare in large quantities and store) for highlites and shading simply take a bit of the basic colour and darken or lighten it a bit.
David Fisher is a worlwide renowned figure painter, sculptor and modeler., he and Anthony mestas even partook in japanese modeling competitions.
For more infos in his skin-tones and techniques you can check his Model Mania Video series.