I'll give you an oposite reply,regarding rhe previous:
Do as the FCOM says, which is APP for the ILS. The airplane will not capture the GS first,as it says on the FCOM,also. After doing flight data monitoring for some years now, I can tell you that one of the most common cause for unstabilized approach is selecting LOC before APP - about 60% of tle flights the crew forgot to select APP and remained above GS (it is not teh normal procedure to select LOC first on the FCOM or our SOP,so it's not standard)
Regarding rudder- yes,you may use it. Monitor LOC deviation, and press easily on the rudder to stop deviation and return to localizer. In this way you'll readjust the crab, and make it easy to stay on loc.
Using roll only you'll get back on Loc, but if you don't change the crab angle you'll end up drifting again..
Use roll ,if deviation is already high.