How to find scientists that cited several of my papers?
You need to first get a database put together of all those who potentially might have cited your work, and the bibliography of their papers.  This is not trivial, esp. if you are in a field where you don't have pre-existing online citation databases for published works.

Are your works available in such a format?  If so, then just do a query which you think will capture all the related papers to your work.  If you are cited in MEDLINE, you can use the "paper like this" as well as exploded MeSH based searches.  Start with the MeSH terms assigned to your work, and spend a little time going over where those show up in the MeSH hierarchy.

Also, how are you defining a specific subset of your papers?  Is this something you know a priori or are you expecting that subsets fall out based on who cited your work?

If your subset is small, and/or you don't have many citing authors, this would  be quicker to just do by hand.  Just build a bibliography from those who cited you (e.g. export Google Scholar/MEDLINE entries, which will have all the authors), and you can then parse that (download them in an XML format and you can probably use XPath/XQuery to do what you need, or see of one of Zotero's report options will help).