Hi Brett, I usually only decant silver and white. The red and black were not decanted at all. I also remember Windy saying red is easy to bleed through. Now I know what he meant.
Skimming off the clear is a very risky matter. It does make the paint more opaque, but it is extremely prone to bleeding through, particularly using dope clear and/or retarder. It works better with a non-solvent (2-part or 3-part) clear.
Many people have come to grief trying to concentrate the pigment in dope. The ratio of carrier (clear) to pigment is about as high as it can be as it comes and still stay together reasonably well. Trying to add pigment or reduce the fraction of the carrier means that the almost any subsequent solvent clear or thinner/retarder will melt it all into a big mess unless it is extremely dry. That's why Windy recommended a 2-part clear over it, instead of dope. He learned that the hard way, I think!
Note that the same effect is why 2-part color, or basecoat, covers so much better, something like epoxy clear can have a far, far larger fraction of pigment than dope can handle. Also why you have to be so careful about spraying it *just enough* to cover. Per unit uncured volume it is massively heavier because it has 3x the pigment. Spray it like dope an you are not going to be able to pick up the airplane. But you only need a little bit of it to cover.
Brett