I have an obj that has texture id’s assigned for things like as fingernails, head, arms etc. I want to be able to mask/select the fingernails using that information, how do I do that? also, is there a way to store multiple masks and recall them later?
Thanks in advance! 
You won’t get that from masks, but you can get it with polygroups. In fact, if you’re using 3dsmax or a similar app to lay out your UVs, you can put various pieces of the layout in different UV spaces, then when you bring the OBJ into ZBrush, if you hit Polygoups>Autogroup, it will create polygroups automatically based on the different UV spaces. So let’s say you have a human model. You can put the head in UV space 1, the torso in UV space 2, the arms and hands in UV space 3, and the legs and feet in UV space 4. Bring that into ZBrush hit Autogroup, and you’ll get four polygroups. You can then use those to quickly hide/unhide specific parts of your tool.
db
Switch on Preferences>Importexport>Import Mat As Groups. Polygroups will then be assigned according to your materials and you can use partial mesh visibility to hide and mask the different groups.
I changed the setting and imported my obj, i held down CTL+Shift and clicked the fingernail of my figure and it didnt isolate it. There is a material ID just for the fingernails. Instead its isolating the entire fingertip which is the regular behavior since it has its own polygroup. Am I missing a step or doing something wrong?
Thanks in advance for any help I really appreciate it!!
-Clay
If you switch on polyframe coloring (Shift+F) you will see if your model has been split into groups.
In order for Import Mat As Groups to work, the OBJ you import must have the correct tags. Whether this is the case will depend on the app you are using and the export options you select in that app. You might do some tests with a simple cube to see if you are exporting the OBJ correctly.
The attached cube shows material groups. You can test this by importing into ZBrush with the Import Mat As Groups on and off (with polyframes switched on so you can see what’s happening!).
EDIT: Conflicts may arise if the material groups are also part of polygroups, so you may need to switch off the Preferences>Importexport>Import Polygroups button to get the material groups to import. You can always re-import your polygroups later by: