ZBrushCentral

Question about Insert Multi Mesh

When i first heard of this feature i was very excited but as i started to use it it became my nightmare. I just dont understand how to use it or when to use it… Im still sort of a noob to the software so please forgive my lack of knowledge.
My main issue is, how do i use it? I was working on a polymesh 3d and as the time came to detail it i tried using it and it said i needed to freeze my geometry… ok, i did that, lost some detail. used it and realised i had lost my lower subdiv levels, I tried reconstructing it and it said it couldnt, i tried unfreezing it and, while subdividing, my computer couldnt handle the calculations and my zbrush crashed. I restarted zbrush and tried applying the object to a polymesh sphere divided to lvl 3, as i tried to unfreeze my geometry my pc was able to do it only my new applied object ( in this case a zipper ) had deformities, holes on the top of every single one of the zippers. So When would someone actually use this? i mean reconstructing meshes is already hard and time consuming and when we do it the new mesh gets torned up, i mean, are we really supposed to apply the details and say goodbye to our lower subdivision levels? how and where can we use this?? Sorry for being such a noob its just i really need this and im very frustrated.
Can someone teach my the right time and way to use this? thanks a lot.

duplicate your mesh. delete lower subD levels.
use the MMI brush(s).
split the original mesh off from the newly inserted meshes and delete the copy.
Now you have a subtool that is your insert meshes and one that is your original.

Hope this helps.

thx a lot, im gonna try this method hope it works