Rails - Jun 2006 - how to save objects in a has_many :through association?

(I posted this yesterday but it never showed up on the mailing  
list... weird.)

I recently converted a habtm relationship into one using  
has_many :through. Some of my old logic relied on the ability to use  
the #<< operator to add items to the relationship and get them auto- 
saved. I''m curious to know the best way to do the same operation with  
the has_many :through configuration. I looked through the list  
archives and didn''t find my answer.

Rather than post my own models and associations, it''s probably easier  
to use the example that Josh Susser came up with in this blog post  
[1]. His example assumes many of these objects are already saved and  
now need to be joined, so let''s change to the scenario where all 3  
separate objects are NEWLY created, joined and saved.

Here''s how I think it would work. Please correct me where I''m
wrong.

# in some controller, assume a form is being passed in to fill out the
# Technician and Skill objects
def add_technician_with_skills
   @technician = Technician.new(params[:technician])
   @skills = Skills.new(params[:skill])
   begin
     @technician.add_skills(@skills)
     @technician.save!
   rescue => err
     # error handling
   end
   # other processing
end

# in technician.rb model

def add_skills(skills)
   begin
     cert = Certification.new(:technician => self,
                              :skill      => skills,
                              # other fields...)
     cert.save!
   rescue => err
      # error handling
   end
end

Will this work? Do I also need to explicitly save @skills or will it  
be auto-saved via the @technician.save! call? Is the cert.save! call  
necessary?

How do I unwind the cert.save! call if @technician.save! fails?

Is there a better way to lay this out so #save failures can be backed  
out?

Thanks for your help.

cr

[1] http://blog.hasmanythrough.com/articles/2006/04/17/join-models- 
not-proxy-collections