The fundamental problem that you're up against is that on any report type or chart a particular Quick Base record can only appear once. So for example, imagine a pie chart, you can only have the project of fear appear once on that slice of pie. The same project cannot appear in multiple slices of the pie.
So one approaches to change from a down and dirty multi select field to a relationship where one project has many Products. If you'd like, you can still roll up a summary field of the different products that are involved on a project so you can have them on a Table report up on the project level. But then you would run your reports down on the child table. The child table would likely be called something Project Products.
He would set up a table of Products, and you already have your Projects table and then you would set up a new Many to Many join Table where one Project has many Project Products and one Product has many Project Products.
Typically, you would then put an embedded report of the Products on your Projects Table.
If you are unwilling to go through that change to the structure of your app, then your own alternative is to put a dynamic filter on the report for your multi select field and select them one by one to count the number of records on the report or see the number of records on some kind of summary report or pie chart.
If you're interested in transitioning your data over to a "proper" child Table with the Project Products, and you need help, post back here and I can help you with any questions you have in building that child Table or populating it with your initial data from that multi select field.
