Basically, after your initial search on SortFix, you can then simply add and subtract elements of your search and see quickly the changes in the results.
Probably the most powerful part of SortFix is the "Power Words" box. According to the site, "these words, retrieved by SortFix algorithms will advance your search in the most significant way."
Give it a try. It's simple and might help you see an important topic you've missed.