Okay so a portion of my mesh has 2 layers of polys very close to each other, I want to mask one side but not the other.
How exactly can I tell Zbrush not to mask the back side??
Again, these 2 layers are very close to one another.
Thanks for your help! 
It was easier in the last version but hereâs what you can try, Iâll go over how to do it in this version since hide and show using selection keyboard shortcuts is not working properly right in this release so you might not get results using the fast method of selection.
Try to select just one small section of polygons on either the outside or the inside of the mesh area that is close together. Doesnât matter which side, just try to go for what is easiest to grab.
Now that youâve made a selection of that area, doesnât matter if you have both sides of the shell selected, then hide the rest so you can only see the one section, start work on this little piece.
Whittle away the selection until itâs just one small amount of polies on the side of the shell you want to protect. This is the hard part in Z4 since to do this you would normally use ctrl +shift + alt to hide polies, but itâs bugged to show all the hidden polies sometimes, which makes you crazy. If you encounter this issue, try another section, and another until you get just get lucky and donât have the show/hide bug.
Now that you have just one poly selected and visible and everything else is hidden, under the visibility menu you will click âgrowâ to expand that selection by adjacent polies.
Keep growing out the selection and hiding unwanted polies (ctrl shift alt drag to hide, but again, itâs wonky right now doesnât always work) until you just have the inside or outside of your shell visible.
Once you have the inside or outside of the shell only visible, click Group Visible in the polygroups menu. Then you can easily protect it or select it anytime you want by simply ctrl shift clicking it and only showing it or hiding it.
Long story short, do what you need to do to make the inside of the shell a separate polygroup than the outside, so you can easily select one or the other. While sculpting, you can use Mask by Polygroups set to 100 in the brush menu to protect the inside of the shell or move it separately etcâŠ
Search for tutorials on hide pt and grow command if you donât understand the method Iâve described. Also if you have issues with hide and show in Z4, you can still do it in 3.5, make your polygroups there, then bring into Z4.
*edit if you donât get it sorted by tomorrow I can work up a visual tutorial, pictures of this would make it clear.