Surgery, use Petsana notes / Kaplan. I dont advocate piracy, but since those notes are a decade old and have penetrated literally every russian, australian, and venezuelan server, use them.
Medicine, WAY too many questions to possibly get through.
However, the UWorld questions were harder than shelf, but easier than Step 2. If you are struggling with shelves, you will struggle with Step 2. Getting some practice is extremely helpful. However, without a knowledge base from some reading during your clerkship, you are going to fail at practice questions.
It is an excellent resource, will prepare you for the shelf, but you must have some knowledge reading other than the questions to do well on a shelf