To do the melee dashdancing you need to dash the same direction twice, but cut your second dash off with a pivot into another dash. You can foxtrot around and do this whenever you want to turn around. I would reccomend practicing it. It can be hardish to always pivot perfectly.
For the platform stuff I did a few different things.
1. Isai dropping still works. You can start your dash animation and cancel it by falling through the platform. This is faster then just landing on the platform and falling through.
2. Platform cancel. There are two ways to do this. One you can hold down and shield as you are passing through the platform to go straight into your shield. The other, you can tap down as you are passing through and it will put you into your standing animation immediatly with no landing lag. If you roll the control stick from down to forward as you pass through, you will immediatly be put into your dashing animation.
3. Platform cancelled shield platform drop. You can still fall through platforms while in your shield like in melee. So you can platform cancel into a shield drop into an immediate aireal. You can also just isai drop out of a dash.
Cool things about this:
The dash dancing is really great for making people whiff moves. Almost no opponent is used to a brawl character being able to turn around right in front of them.
The platform stuff is insane. You can use it to increase your speed, range, mobility, defense, reversing bad positions ect. It is the fastest way to fair behind you when you PC then pivotdrop fair. You can really confuse people and make marth really ****ing hard to hit.
There is a ton of more uses, but I am typing on my Wii-mote haha. I will let you guys discuss that
.