Might be tough with a camo net... but try this
Make a copy of your Camo net layer (or whatever you want)
Make sure the copy is Below the original Camo net layer
Hide the original Camo net layer
Select the new layer you just made
Select from the top menu -> Filter -> Stylize -> Emboss
Play with the settings (use small values)
Un-hide the original Camo net layer
Set Blending mode of original Camo net layer to Overlay (try different options)
Adjust the Opacity/Fill of the Embossed camo net also.
OK, this isn't technicaly a "bump" map but it does the same thing, uses another image to create a false 3d effect.
Search online for tutorials and also look into the "Displace" filter (Filter -> Distort -> Displace)
To use this filter you need to save the Embossed Layer as a completely different .psd file, then import it when called for in the Displace Filter process.
I've gotten very good results using thess techniques on things like brick walls, vehicle details, uniform seams and patches, etc...