After bashing something, you can hold grenade in order to get a lot of height or go really fast in one direction. For some reasons, this only works if you also have Grapple even if you don't have to use Grapple at all. You also need to prime a grenade before bashing or you'll decelerate after your bash.
You can't bash your own grenade in order to setup this trick since pressing grenade after your bash will result in your last grenade exploding rather than Ori charging a grenade.