There's no such thing as 'not being good at spec maps'. If you understand them, it's straightforward. Black=no spec, white=very strong spec. Things get slightly more complicated with the inclusion of a glossmap, but let's assume you're not using that here.
What you want is a contrast between different surfaces, and to emulate the way light affects different materials. This is also the map where you add subtleties like fingerprints, grease, scratches, etc.
Overlay your ao map as darken layer, as there should be no (or very very little) spec in crevices where dust settles. Add scratches to things that stick out and are most likely to scrape against other surfaces. Play around with contrast a lot! An overly subtle specmap may as well not be there.
edit: if you're saying it's lighting the wrong way, you've probably got an inverted channel, maybe two. It's relatively hard to tell in these screenshots though, since there's no spec. Increase the spec and try flipping your red and/or green channels in Photoshop.
Also, can we see seperate diffuse- and normal-only screenshots (on the model, I mean)? It appears to me that you're highlighting a lot of things in your diffuse that are actively working against any normalmap you have. On a lot of edges you have a white line, then a black line, then another white line. This is effectively killing any opportunities for showing off a nice specular highlight, which is a big part of convincing metal.
Last edited by MightyPea; 06-23-2010 at 04:35 AM..