Maintaining 'stable' and 'development' versions of a repository (hopeless newbie question)

Dear fellow Bitkeeper users,

I am still but a young software developer newbie, so I hope someone a little
more experienced than me can help me figure out how to do this.

I work on a small research project where me and several others are
simultaneously working on a simulation.  The simulation code is very
processor and memory-intensive, and tends to only be run by scientists who
Know What They are Doing and also know how to validate the results.

I've decided the best approach to developing the software is to keep a
stable repository for actually running the simulations (bug fixes only) and
a development version for gradually moving cool new features into the stable
version.

I want the stable repository to effectively be a few changesets behind the
development version, with the ability to push changes in the development
version to the stable version on a changeset-by-changeset or file-by-file
basis.

The problem is, I don't know exactly how to do this in Bitkeeper (I wouldn't
even have a clue how to do it in another tool), or perhaps I'm taking the
wrong approach.  What I've done so far is to to create a clone of the
development repository and call it stable.  Then I pushed a bunch of great
new changes into development.  What are my options for pushing changes from
development into stable?  I don't know what Bitkeeper commands would allow
me to selectively pick changesets from one repository on my system and apply
them to another.

Forgive me, I'm actually still really new to the version control game, and
I'm not sure I'm even using the proper terminology.

Best wishes,
~Aron