Changing base audio volume levels ?

My code used to use AudioDevice->GetSoundClassPropertyMap() to iterate thru the audio classes. This was done in response to a user moving a slider to change things like the master volume or SFX volume. However, since updating to 4.15 I’m getting warnings that you’re not supposed to use GetSoundClassPropertyMap() any more. It’s been replaced with SoundMixClassOverride something or another. Unfortunately, this new fangled system is poorly documented (from a c++ view anyway). So how does one do basic volume levels changes for Master, Music, Voice, SFX like you used to?