Does GF Milk Paint require primer?

GF Milk Paints are self-sealing so it is not necessary to use primer.

You may use a white pigmented stain-blocking primer if you need to cover grain, paint light or white color on dark wood, or if you're painting a wood that is known to bleed, such as pine or mahogany. We recommend using General Finishes Stain Blocker, Kilz or Zinsser white pigmented shellac-based primers.

Warning: sometimes it is impossible to block bleed through. Always test. Not all projects with existing finishes are candidates for light paint colors. If this happens, start turning your thoughts to Lamp Black Milk Paint - that will cover a lot of problems.