Me being a person who always uses DDKK, I can let you players in on a few tricks I figured out when streaming tons of d's or k's. Only been playing for a little more than 2 months.
Like, when I am tapping fast streams of one color, depending if it switches to another color or not, I use both my index fingers on the keys with the appropriate color. I use the zxcv keys to do DDKK, I know it is super awkward to play with your hands uptight and sometimes rubbing towards each other, my hands aren't very big so the space between my hands when I play is almost as big as doing something like zxnm, askl, or even qwop. Another trick I have for myself which is more of a preference I think, I look a bit to the left of the middle of the game screen, so I can read a bit better. You would be curious how I can time the notes when my eyes are barely looking at the judgement circle where you hit drum notes. I just seem to have a bit of skill to do that.
Now, if you wonder if I always try to hit the big D and K notes, there are many circumstances where I don't do so. Many cases include the Taiko Oni of Freedom Dive, or if there is a stream of D and a mix of little d in that too. An example myself would be similar to the last stream in the aforementioned beatmap difficulty:
dddddddDdddddddKdddddddK
For this, I just hit the big D notes as if they are regular d, as my hands can't stream D notes unless the note per second speed is a bit slow, like 5-7 D or K a second is near my max.
I don't do kddk at all, so I can't really tell you anything about using that scheme.