I use baby powder as dry shampoo (and it works GREAT!), the talc kind, but my hair is dark blonde in some areas and light blonde in others. Even some brunettes can maybe get away with it, if you rub it in and then blot it out.
However, I don't like scents at all, so I looked into alternatives. Apparently some brands of dry shampoo are made with rice flour or rice starch (whichever is the finest, used for baking I assume), with a few other ingredients, so I assume you can cut the other ingredients out? And I also read you can use corn starch. So I am presuming anything very fine textured and "flour like" would work.....I thought about buying rice flour or corn starch at healthfood store, to use instead of baby powder, but never got around to it.
I think talc powder makes some people sneeze, and I heard women who use it "down there" have higher rates of cancers of that general area.....though still very small risk...so I may change eventually (even though I don't use it down there, but it scares me to think I'm breathing it in), but right now I do like the talc baby powder. I think dark hair could probably get away with it, because you can brush or towel-rub it out. It works by literally soaking up the grease!!!!!!
Also, I noticed if I don't take my fish oil, I have way less oil on my scalp and can go another day without washing. But I feel the fish oil's important. I think any oils can leach out of the scalp, you may notice if you take a lot of oils. But they are so important!
I will wear a baseball cap too if I have to go out in public and my hair is greasy, and I am too lazy to do baby powder. I just only have the energy for a certain number of showers per week. When I have bad body odor, I use alcohol swabs used for pre-injection, and wipe under my arms.....for me it doesn't sting. I like them because they kill the germs that cause the odor and aren't loaded with scents. Then I will use acne pads on my face and back. Complicated, I know....but I am seriously fatigued.