Conditional Dashas - When to use them?

Hi Ernst and all, 

In BPHS, Parashara gives more than a dozen different Nakshatra Dasha systems, each for different cases. Parashara also says that Vimshottari and Yogini are general case dasha system which applies for all. 

Now, my question is - when do we use conditional dashas like Ashtottari and Shatabdika when analyzing someone's chart? Do we use those dashas side by side with Vimshottari and/or Yogini, or do we use them independent of Vimshottari for charts where those dashas are applicable? And do we use the same principles and techniques that we learned in Vimshottari course for analyzing the conditional dashas, or are there any special rules and techniques for analyzing them?