Here are the instructions:
Trailer single crochet (tsc): insert hook in front loop, yarn over and pull up loop, yarn over and draw through one loop, insert hook in back loop of same stitch, yarn over and pull up loop, yarn over and draw through two loops, yarn over and draw through remaining two loops.
Trailer half-double crochet (thdc): yarn over and insert hook in front loop, yarn over and pull up loop, yarn over and draw through two loops, yarn over and insert hook in back loop of same stitch, yarn over and pull up loop, yarn over and draw through all four loops.
Trailer double crochet (tdc): yarn over and insert hook in front loop, yarn over and pull up loop, yarn over and draw through two loops, yarn over and insert hook in back loop of same stitch, yarn over and pull up loop, yarn over and draw through three loops, yarn over and draw through remaining two loops.
These stitches will be taller and wider than regular stitches, so you may have to alter patterns to make these work. Here is a swatch to show the difference in the puffiness. You can see the fuschia-colored hat very well through the rows of regular double crochet. But see the texture and thickness of the trailer stitches? There is almost no color showing through. If you could feel it, you would love it. It almost has a spongy texture. Make sure you click on the image to get a close up. Comments and feedback would be awesome! Even if you don't like it. ;)