Great question, @AnUpsideUpWitch! Thanks for bringing it up- hedge witchery is a fascinating topic, and it looks like you’ve got some very helpful answers to get you started 
I agree with Francisco- astral projection may be just what you are looking for in regards to spiritual travel 
You may also want to look into lucid dreaming as well, as dream magick can also be considered part of hedge witchery and it involves both spiritual exploration and deeper travel.
To learn more about lucid dreaming, you can visit this discussion talking about astral travel vs. lucid dreaming, the previous challenge about Dream Magick, and this Lucid Dreaming App.
Good luck with your learning and please keep up updated on what you discover! 