what specific issue you are having with CR ? Are you following the standard procedure of getting the Conclusion and then looking for asumptions model ?
I guess you dont have a lot of time , else CR bible or MGMAT's CR book could be a good help. MGMAT's book is easy to go thru in less time, you might like to get a copy and try it. It helped me with Assumption stuff, and mostly CR is all about being able to see the assumptions.
let's know the specifics you are having trouble with.
As you said I am going though MGMAT's CR and I think it will be great help to me(I was not fallowing right standard procedure as you pointed), I got MGMAT- CR and RC-Ch-1 to 3. on-line, So let me got throught it and I will post here after I finish.