change branches in shared repository from trees to no-trees

I moved my project repository from subversion using the svn2bzr tool
My repository consisted of trunk and 1 development branch, which both have been converted into shared bzr repository with working trees. I merged my dev branch under bzr into the trunk and now, after cleaning the trunk tree, I wanted to start working on the project using bzr.

This is a web project and it would be nice to be able to see different branches in the web browser, because I'd like to work on a few things at one time. After reading the docs, it looks to me, that it would be better to maintain a no-trees shared repository and instead of working on the trees in the repo, I'd better work on the checkout in the selected directory, which would be also pointed at in the virtual host configuration. If I'd want to work on different branch and see it in the web browser, I could use bzr switch in my work dir. Is that correct? Now, I'm scratching my head, how to convert my trunk branch (the other branch is not important, because it's life ended) into a no-tree branch. It's probably an easy thing to do, but I couldn't find any information about it and I don't want to destroy anything. Lot's of info about starting branches etc., but lack of info what to do when you already have branches etc.

I would also like to change the default of my shared repo from trees to no-trees, so I don't have to remember it when creating new branches (which should be no-trees).

Thanks in advance