Hi all, just joined the forum, so let me start by say hello and thanks to all the amazing zbrushers out there.
So let’s get to it!
I’ve just started getting into uv s and texturing in another program, when I import the texture and apply it to the subtool, I can still change materials, that’s what I want! I make sure mrgb is on, add is off and fill abject, easy… Until I switch to another subtool and change materials, the original subtool with the uvs changes too, even though I filled object and mrbg was on!
Any ideas?
Cheers, a frustrated noob 
If you have a texture applied to the subtool, you have to fill the texture with the material you want. Go to “Tool > Texture Map > Fill” and with your material selected, click “Fill Mat” button. Then the material will remain on that subtool.
Cheers, thanks so much, I knew there must be something I wasn’t doing 