I've yet to memorize Mattress Stitch.
Like grafting (kitchener stitch), it's just something that hasn't yet become automatic.
However, since I have to seam my Marian Cowl (the pattern is written in-the-round, but I don't have any 12.75 mm circulars, just straights), I wanted something that would be close to invisible but not too heavy.
So, hence my searching for a tutorial on Mattress Stitch.
And, once again, Knitty came to my rescue. They have a wonderful tutorial on Mattress Stitch that I currently have open while I seam.
. . . I love the internet. Just having this information at my fingertips with a simple web search is -amazing!-
However, I should return to seaming. I'll try and get pictures of the finished cowl once I get daylight tomorrow.