I recently did my FAA IR in a GNS430 equipped C172, having done most of my instrument flying historically with steam driven equipment in the UK. It became really apparent really quickly the need to be utterly on top of the avionics in terms of modes, thinking ahead, tricks, and so-on.
My solution was to download the G600 trainer to my laptop and pre-run every planned flight on that, with lots of mucking about with modes and options to get a good idea of what I could do. It's time consuming, but necessary. I found that I did need to manage this for myself, as instrument instructors do not generally seem to have much idea about aiding students in guided learning of these systems (that surely must change going forwards).
I think I'd recommend exactly the same approach with any advanced avionics system now. Just doing the old fashioned stuff for the moment really does not work - you need to be fully on top of the kit from the start. For example, knowing how to load up the GPS visualisation of a planned VOR approach to aid your SA, it is just how you have to use it.
G