I used a regular 1/4" seam with a straight stitch. I have a mid-arm machine and frame that I used to quilt it.
The Too Cool methods recommends quilting each block differently, depending on the design of the shirt, but I'm not that experienced yet in quilting on a frame, so I used a pantograph for an all over design. I used Superior's MonoPoly clear thread to quilt it, which also went much better than I expected. It was the first time I used MonoPoly thread and was very happy with it. previous attempts with clear nylon thread were horrible! I think as long as you pin the sandwich well, you shouldn't have any problems.
I'm happy to share my experience with it. It was alot of fun.