Shading camo?

Im going through the same issue with a Tamiya 1/16 elite infantry figure. This figure is wearing the Pea dot camo and I was also worried about how to shade it. I used Testors MM oils for the camo (deep brown base various greens and khaki). I then waited a few days while finishing the other parts and the soldier's gear before going back into the shading part of the clothing. I just ended up using the same colors I used for the camo and mixed them together to make a neutral color and drybrushed the raised parts of the folds with this neutral mix. It ended up working quite well and didnt "pick up" any of the camo I layed down previously. Im still finishing up the figure and I think Ill do an overall wash with dark brown/black mix in acrylic when its done. I hope this helps G/L!