After applying basecoats I like to differentiate all the different panels and such with various filters. When I finish a model with a camo pattern, am I wasting my time with the preshading or should I perhaps wait until I apply my basecoat and apply a camo pattern before I start to differentiate the various plates and sections of the model?

Good question, Michael. Expect to get as many differing opinions.

Unlike with a uniform base color, I find with camo it's nearly impossible to get uniform opacity of the different colors without completely covering up the preshading. I prefer post-shading when doing camo. After applying each successive camo color I will typically highlight the borders of the pattern and any panel lines/details with a different color, typically the primary color with the tint slightly modified. Need to experiment a little for any given color to find the effect you like best.

That is of course only one opinion, and there are people with different techniques achieving much better results than me.