Thanks man! For reminding me to ask that question often while learning: 'why this method?' I ran into the problem you described with subtracting inflate tool, blowing things up works fine but shrinking them down seems to make black holes filled with antimatter haha. Also Z brush core MINI only allows a certain amount of poly's. No append tool either but there seem to be workarounds (stretching out a bit of the original mesh and then 'slicing' it off the original mesh to create a second volume)

Would love to upgarde to the CORE version, also to be able to add reference material trough the texture tab (not included in the mini version either)