I did not use Sketchy at all. I tried but after a while I found it a bit annoying and started forgetting what was in which image! I occasionally used some reference books (or even just googled) stuff when I wanted further explanation but that was really it. UW plus referencing FA really seemed to cover most of the material very, very well. The only things I found those resources lacking in were images (gram stains, autopsy specimens, etc).
At least on the test I got, the questions that couldn't be answered from those resources were mostly either bizarre ones that would require PhD-level knowledge or just extremely particular details that go beyond even the level of regular review books (eg, BRS, RR,...). I am pretty sure those questions made up less than 20% of the test.
In fact, I found myself missing multiple questions (at least 4 that I can remember) that I should never have missed as they were UW material so whatever score I end up getting, it could have been higher had I: learned UW better and/or got more sleep/focused better on the test day.