Once you obtain Bash you will nees to "climb" back up the way you came by bashing off purple projectiles. The one that is firing horizontal is quite easy to just get on the right side of the screen then Bash upward off one, Jump at the peak of the bash, bash of a 2nd as it approaches, jump, and bash off a 3rd. You dont actually have to "juggle" the projectiles themselves, just bash off 3 or 4 without touching the ground. This spot is easy to bash off of them indefinitely without stopping.
This achievement can be seen in my collectibles video below at 7:23.
Solution will be updated once final collectibles video is done.