In my experience, you should at least read through all the instructions and follow those that are applicable.  Each user's situation will differ but given the fact that each new iFix contains all prior iFixes it is highly possible that some of the instructions will have already been implemented if the earlier iFixes had already been installed.  Repeating those again won't hurt - but would certainly be unnecessary.  For me - unless I am positive that the changes in the current iFix match those from a prior one - I just follow all of the steps. 

Also - always be sure to perform the repotools-xxx -clean command for every application you have installed.