hey spatzi!!! DEPENDEDNT ON SURFACE YOU ARE WORKING ON, SOME OF THE BEST ERASERS ARE THE FABER CASTELL PERFECTION, THE PINK SOFT ONE AND THE WHITE/GREY/BEIGE, oops just looked up and realised i had caps on!! too lazyto type all that again!, as i was saying, faber castell perfection they are called, initial layers want to be thick paint, very little water and no medium, get the shapes in, the dark shapes with a mix of umber and red ocher, then scratch and erase, then get your mid layers in with red ocher only, again relatively thick, scratch and erase any small highlights, then glaze. this will give you both volume and depth. this is a little trick using household items to spray across/through that helps with hair.... things like garden wire/ties or copper wire.... you can work out how to do that yourself though.