sorry had to start doing some stuff for work.
this could just be a long running challenge for people to practice texturing.
here are some instructions i've made on how to do rusty scratches.
take 3 images, I have a base metal, rust and some metal scratches.
copy and paste the rust onto the base metal as a new layer
add a layer mask
go to the scratches image and desaturate it, then crunch the levels so you have a high contrast. Now select all and copy.
go back to the rust and metal pic. click on channels and show visibility on the layer mask.
paste in the contrasted scratches. (i have inverted the image too)
if you hide the visibility again and tidy up the edges. you should have something that looks like this.
obviously you can work this around what you need to do.
hope it helps.
one more thing... does everyone know how to daisy chain bump maps?