Walk forward once the fight starts and throw the boomerang right before you jump off then pull your sword out in midair. Do one roll out of the fall slightly right then instantly jump attack Dangoro, he will then curl up and you can sidehop to equip the Iron boots on faster and throw him in the lava.
Below is a video of fighting Dangoro with roll stabs for all the hits. The first hit is slower than mentioned above but the second and third has audio ques to listen for.
For the second hit wait until the first beat stop playing.
For the third hit wait until just after the second beat starts playing.
Jumpslash 3 times from the spawn position, then backflip 3 times and equip Iron Boots during the 3rd backflip. Keep holding L, and wait for Dangoro to hit your shield. Let him nudge you twice, then grab and throw him. If the grab is too early it won't work, and if its too late Link will fall and grab the ledge. This method saves about 5 seconds over a normal fight.
You can do the same thing with Ball & Chain. Jumpslash from spawn position, then throw the Ball & Chain immediately to make Dangoro start rolling. Put on Iron Boots and roll straight down once. Tap Up to make Link face him, and time an A press to grab and throw him.
After doing the Instant Second Hit, Dangoro bounces on the lava for long enough that you have time to attack him before he lands again, forcing him to land preemptively with his roll charge attack. This saves an additional 3 seconds over allowing him to land regularly, however he doesn't always bounce close enough to Link for this to be possible.
It should be noted that in 100% which will have shield bash, you can use shield bash to make him expose his stomach so you can spin attack him to make him curl up, this is faster than waiting for him to attack if you mess up the strategies mentioned above.