It's not too hard. The optimal way to do it, as far as I can tell, is to input a dash, let it play out until you're almost at the end of its range, then do a shield and input another dash as quick as you can.

There is a little bit of a delay on when another dash can be put in, but you're basically just waiting to see the shield reach the chest.

Once you get the timing on it, doing it a bunch of times in a row has a gallop-like rhythm to it.