In my day the sensible approach was to gain a multi engine rating in VFR, the do the Multi IR. I have to say I did my multi engine rating just before the minimun time to do a multi engine rating was ten or fifteen hours, I did the multi engine rating and teast in less that four hours! Therafter I did the multi engine IR, initial on singles, then on multi engine types, with very little sim time. I have to say the way I did it was the very best and relatively inexpensive.