How can I print the contents of a VSFlexGrid control?

Use the PrintGrid method.

To add advanced features such as print preview, or include one or more grids into a single document, consider ComponentOne's VSPrinter control (part of the VSVIEW product). The VSPrinter control has a RenderControl property that you can use to print grids of any size. This method will also allow you to control page breaks, create repeating headings, and preview the document.