Dander is tinier than dandruff. You can easily see dandruff, but not dander. If there is just a little dandruff, you can use a slightly damp cloth to wipe your cat's fur. A grooming session will help, with a bath, drying and deshedding. I bathe my short-haired black cat about once a month. I rarely see dandruff.
I would love to give Diesel a bath however he's already a big scaredy cat, always hiding in cupboards He's a pretty big boy, 12 lbs so I think a sink shower is out of the question, it'd have to be in the bathtub. How do I successfully hold him down for a shower?
A friend of mine has a black show cat who gets dandruff from stress. She wipes him down with a cloth dampened in Listerine just before taking him into a ring. It works really well, but it's a temporary solution and I wouldn't want to do it too often because I think it probably dries out the fur.
When we first brought JC ( black dsh) home he was very stressed from the shelter and then being in a new home. He had a lot of very visible dander. Luckily he loves to be brushed so between that, a couple waterless shampoo treatments, and settling into his new home, the issue resolved itself.