Was always told never to blow air inside the machine, it pushes the lint further in and places that you then can't reach. My sewing machine book also stated the same. I remove the bobbin then the bobbin case and it exposes holes in the bobbin case holder. I use a small brush that came with my sewing machine, I poke in the holes slowly and lift out the brush, it catches lint small pieces of thread. I clean mine out after each quilt.