In tab, the Swiss Army Knife strum looks like this:
A few elements make this strumming pattern more interesting than some others. The first is obvious when you write out what you’re actually strumming: down, down-up, up-down. Yep, you’ve got two up strums together. So after the first up strum, you need to move your hand down without hitting the strings.
If you’re counting, you have to count: “one, two, and three and four.” But you have to remember not to strum on the three.