@Dave22152: One of the things I did to help myself was use a difference blend mode to see what is actually happening while you change the settings, 'cause it’s not always easy to see looking at the image (especially the chroma tab changes).
Although this post only concentrates on the luma tab, it can also be used with the chroma tab.
Knowing about the details of it all is rather important, so do follow @Claes’ advice.