i have been trying to solve this for hours, i have sculpted a head and now i have painted it, but then i wanted to paint some material in on the eyes and stuff like that, but i cant figure out how to get it to paint the material, all it does when selecting material is to switch the whole tool into that material 
im so thankful for any help
In order to be able to paint on your subtool, it has to be filled with a base color and material first. Select your base color and material then turn on ‘Mrgb’ button then go to ‘Color’ menu and click ‘FillObject’. Now you can select a different material and/or color to paint with. If you just want to paint a different color then turn on ‘Rgb’ button first. If you just want to paint a different material then turn on ‘M’ button first. If you want to paint a different color and material then turn on ‘Mrgb’ button.
Thank you so much!