Spreadshirt design guidelines dictate that all lines and elements need to be a thickness of at least 1.5mm. They suggest you can verify this by:
using a 1.5mm dot (punctilio) to mouse over the thinnest parts of your design and 1.0mm circle to mouse over this space between the lines.
How can I achieve this in Illustrator CS6 Mac?
Additional info: I also need to do this with expanded type, not just single paths and shapes.