We don't have any real problems using Matthews Brushed Aluminum. I assume that it is the 43412SP color being discussed, a factory pack color that we buy premixed.
It seems to cover well and no under-color is required, though I handle it a little differently from the standard colors, as I do all the metallics.
First, I apply two medium-wet coats, using the appropriate speed reducer, with a flash in between. I then finish off with a third, mistier coat, at an increased distance from the piece. Sometimes when I lay down the two wet coats I can get some mottling, common to metallics. This is the flakes trying to separate and/or float. But the final coat applied slowly on top of the two still-wet coats should yield an even velvety metallic that is not dusty looking or sandpapery to the touch.
Whenever I got runs, it was because I was laying it on too heavy trying to avoid dustiness. Now, I usually slow the reducer mix down a little and don't have my gun as close. A little slower on the gun movement as well, with the fan a little wider. If it's done right, you should get even flake distribution and it should still have a little shine, with no dustiness.
So, not too heavy laying it on, but not too fast of a mix so that it can still "meld" together.
By the way, all three speeds of Matthews reducers, and the retarder, can be intermixed to fine-tune the speed of the mix.
Also, I feel it's important for the metallics to spin on the mixing station a full half hour every morning. If I am going to spray metallics in the afternoon, I will spin the mixing station again for 15 minutes before making the metallics. And all the metallics, both the factory packs and the base colors, should go on a shaker before being put on the mixing station. If you don't shake them first, you will probably find a pile of flake when you get to the bottom of the can, flake that never got stirred into the mix. I expect this settling changes the color slightly and may contribute to a little loss in coverage. The mixing station alone is not adequate for thoroughly mixing the paint when you first get it, especially the metallics.
The Brushed Aluminum color was developed, I believe, to simulate Alcoa's anodic aluminum color, just as the 41313SP Dark Bronze was supposed to mimic Alcoa's Duranodic Bronze (Duranodic was originally owned by Alcoa as a trademark).
Both colors can be mixed from Matthews base colors but are available as factory packs, too, which is convenient. We use both colors extensively.
One more point, and everyone that sprays Matthews already knows this—the paint-to-catalyst ratio must be exact. The addition of the accelerator, if you use it, must be exact, too. You can fudge a little on the reducer content, but not the catalyst or accelerator. I even bought a stand-up test tube at the science store for measuring accelerator in tiny amounts for small batches of paint (sometimes less than 3 ounces of paint for small jobs). The test tube is marked in milliliter gradations.
Now, having said all that about metallics, we do not use the Low VOC line of colors. Their handling characteristics may not be exactly the same.
Brad in Kansas City