I think a good method is mixing different techniques. Till now I gave each canvas covered fuselage a postshading with Tamiya or Gunze smoke. More prominently on the aereas that were stained by castor oil. I covered the ribs and strings with thin stripes of masking tape. After removing the masking tape I am used to add a little more smoke on those aereas where the castor oil soakes the fuselage from the inside (this is what happened to Fokker E fuselages e. g.). Last step is using dark brown/black oil paint and to brush it over the soaked aereas to add some different color. No wash, just to the contrary: thick color that is more or less rubbed into the existing coats of colors. You can use stiff dry brushes to remove paint, if you need to. Using this way you can easily control the process and avoid overdoing the process. If you should use linen decals, I'd use them after the shading with smoke and before the use of the oils.
I hope, that helps
Borsos
