I try to include a total screen failure, manual raw data ILS on the ESIS (S/by horizon system) when doing a TR on the 139. It is primarily a way of convincing the candidate that the instrument is easier to use than they might initially think and is a confidence booster. The ILS is a usually a bit ragged but as HC so rightly says anyone who has trained on a basic ILS system retains that basic skill to a level that will get you home safely even if it might make the IRI cry a little.
Just read HC, next contribution and have to agree wholeheartedly