CFI-I practical
The CFI-I practical is basically an instrument ride out of the right seat. The oral will be much more in-depth, and, of course, you will have to prepare a lesson plan.
Know the FAA Instrument Flying Handbook forwards and backwards. Know primary and supporting forwards and backwards. Know the gyro instruments and pitot-static instruments forwards and backwards. Know the AIM, charts and regs. Know and be able to teach radio navigation and holding. Know ADF. Also, be prepared to answer FOI questions. Although you've already demonstrated FOI knowledge during your CFI initial, some examiners still like to test it on subsequent CFI add-ons.
As always, the PTS will give you what you need to know and the FAA materials from which your practical is drawn. You will be responsible for the contents of those materials.
Oral could take a couple of hours. Flight should run something like 1.5. Of course, do not stop teaching until the examiner signs your Temporary and hands it to you.
Hope that helps some more. Good luck with the practical.