Tamiya base paint before Tamiya metal paint

NunoCardoso

Maybe because they are using enamel, and I am using acrylic, maybe I thinned too much, but it was just a grainy mess.

The enamels seem to brush better than the acrylics, which have a tendency to lift underlying paint. 

Tamiya's metallics can be a bit fussy to airbrush smoothly as the metallic pigment particles are heavy and tend to clog the airbrush quite readily.

BlackSheepTwoOneFour

Tamiya don't make enamel paints. Only acrylics or lacquer.

Actually, they do. They're just not widely available in the US. 

https://www.tamiya.com/english/products/list/enamel_1.htm

NunoCardoso

Maybe because they are using enamel, and I am using acrylic, maybe I thinned too much, but it was just a grainy mess.

Tamiya don't make enamel paints. Only acrylics or lacquer.

If you are trying to do the engine turned finish, the effect with the overlapping circles, it is very hard to paint the circles properly with an airbrush or even a regular brush- they are so small even in 1:32 scale.  What I do is use a homemade (inkjet decal).  I do the array of circles with a light gray color in my graphics editor (like Photoshop, though I use a clone, not PS).  The decal does make the surface glossy, but then I dull it down with a dull clearcoat.

Here's a thought you might try, using the Tamiya Flat Aluminum. I've used the shiny NMF finishes from several of the acrylic lines of other manufacturers, they look really good, but some are not as durable as I'd like. Handling can damage some while finishing assembly, decaling, etc.

I agree, the Tamiya flat aluminum is grainy and needs work. Just experimenting with it, I found the fine polishing pads work wonders by leveling the gritty look, and leaving a fine, realistic polished aluminum appearence. The level of polished look is easily adjustable, either by grit of polishing pad, or time spent buffing. It polishes easily and very quickly.

I also find that even though I customarily prime the model with Stynylrez, (I know, a strange name,) the flat aluminum works well with primer, or without.

My process is to polish to desired level, then a coat of Tamiya clear, adusting polished look by using whatever combinations of their clear finishes works. I use only their X-20A, and combinations of gloss and flat as my clear mix. My favored thinning ration is 20-30% thinner to paint.

Worth a try, I'm sold on it and continue using it. If you feel like it, let us know what you think of the results, others might want to try it.

Patrick