If you have a current ATPL with IR, current FI Rating with the 'no applied instrument' restriction removed, plus current MEP and SEP Class Rating, the additional training and testing you will need to instruct for the CPL and IR will be.....
Nothing. Apart from FTO in-house standardisation, that is.
An IRI Rating is only applicable to non-FIs who wish to instruct for the IR, you do not need one.
And CAAFU haven't existed for over 10 years, by the way!