The 'Big 5' databases are where users should definitely start their research journeys. These databases are best used for what I would call Background Questions; broad questions that arise when you need general knowledge. Answering these types of questions will provide an overall understanding of the clinical problem you are learning about and help develop the well-focused foreground questions that come up at the point of care.
At the beginning of the research process when you want to know the lay of the land or when conducting literature reviews these are the databases you will want to start with. For any medical scholarship project these databases are where you should focus your time and effort.
I would strongly suggest starting with PubMed AND Embase and then choosing one of the other 3 databases to fill in any gaps. PubMed and Embase will give you the majority of the unfiltered primary and secondary literature necessary to fully understand and write about a topic. Once you have a proven search strategy and relevant keywords round out the research using Medline, Web of Science, or Scopus.
These tutorials are meant to be quick dives into the background and search features of these databases to give you, the user, the ability to navigate through to the best evidence/answer possible. All tutorials are about 15-20 minutes.
Materials and research produced by organizations outside of the traditional commercial or academic publishing and distribution channels. Common grey literature publication types include reports (annual, research, technical, project, etc.), working papers, government documents, white papers and evaluations. Organizations that produce grey literature include government departments and agencies, civil society or non-governmental organizations, academic centers and departments, and private companies and consultants. (Wikipedia). Below you will find some places to look for grey literature.