it's not that hard.....
First what size will you go to? 7gal, 10gal, bigger than that?
here's my method. but other growers have other ways so you can ask around........
Squeeze the sides of the bucket all the way around. pushing in the roots and dirt leaving a slightly empty space between medium and container.
While holding the stalk, tilt the plant on its side. and pull.
NOT HARD you WILL rip your plant up if it's got any weak spots.
Pull and rotate the bucket at the same time.
takes some practice to get used to but, it works for me very well...
As soon as she is almost completely out, use both hands to reach into the bucket and grab the whole entire mass of soil and roots.
lift her out and stand her up in the new bucket....... fill the empty space with new soil/soilless medium, and water.
That's just how I do it. I'm almost positive I make things a lot harder for myself than they have to be. but I like to do things differently sometimes lol