Note: Its a very good idea to name your layers. You can change the name of the background layer by double clicking it. I've named my layers 'metal tex' and 'metal colour'. Not very imaginative but I know at a glance what they are.

So now we add another new layer above metal colour. I've named this layer 'paint'. Fill this layer with 10,119,90. If you click on the little arrow on the far right of the colour tab & change to 'HSB sliders' if it isn't set already. Now we'll do a little painting. I used a large round brush (65) & painted some splotches on, using the HSB sliders to change the colours:

I then added a Gaussian blur, with a radius of 5 pixels.

Those splotches are looking too distinct. What I did to remedy that was to use the burn tool (65 brush again) on the light parts and the dodge tool (same again) on the dark parts. NOTE: I never use either of those tools on much more than 15 - 20% exposure as I feel its better to start subtle & build up, rather than have it higher only to find its too much. After that I used the blur tool (100 brush) on the whole thing & just smushed it all around until I was happy.

Ok, add a little noise again, somewhere between 1 & 2. I generally stick to Gaussian, but this time I unticked the monochromatic box. Play with it & see what you prefer.

Rule 3 of texturing: Chaos = real. Randomness including splotches, tonal shifts, noise, water streaks, dents etc all add believability to a texture. Go outside & look at where dirt collects on surfaces & where scratches & wear occur too. Take pictures if you can. You'll also get some sunshine & fresh air to boot!

Here's where it gets a little tough if you don't have the 3d total texture CD. Its time to add some grunge layers. The CD contains a number of grunge maps which are invaluable in creating dirty & worn textures. I'd recommend the texture CD, as it's good value for money & no I don't get commission. You can probably find some on the net for free, (I have)& its a good idea to build up a collection if you can. Failing that, you can create your own, either by taking pictures of dirty surfaces and then altering them in Photoshop by making them monochrome & playing with the levels, or you could paint them as well as using filter effects like noise or horizontal grain for instance, to enhance them. A word of warning - don't just use the clouds filter. It produces random fractals each time yes, but on the whole its easy to spot & doesn't produce great results. If you want to use it, my advice would be to use it in conjunction with other filters like noise or difference clouds, (try running that one about 8 to 10 times for different effects.) or hand painting as well. I generally only use it as a layer to alter the hue or saturation of a colour layer below by using blending modes. It's not just me saying this - Alex Lyndsey from DVgarage.com (an ex-ILM employee) says the same thing. Incidentally DV garage sells a grunge pack too - the surface toolkit, but its fairly expensive for the average artist. They do do some video tutorials that show how things wear & get dirty & what to look for when creating textures for free, which are worth checking out.