The chance for a particular mutation isn't more or less depending on whether it's neutral or not. They are all independent events. What it does mean is that the phenotypic expression moves in chunks. You can see how, at the simple level, a group of two mutations can move en block into a selectable feature. The demand for the selectable intermediate is removed. Even greater steps are taken at the protein level. Now, add the hierarchies and networks where a single mutation can effect changes for multiple features and you can quickly see how big morphological changes can take place without selectable intermediates.