Step 1. First learn to swap two balls in hands almost without looking. Keep your eyes straight ahead, above the two balls.
Step 2. This two-ball excercise is more difficult than it looks. Rehearse.
Step 3. Juggle with very high throws keeping two balls in hands as long as possible (Siteswap 522). Every once in a while, swap the two balls that you are holding, thus juggling Siteswap 531. (See Lesson 5 for Siteswap notation.) You need to see the peaks of both the 5-throw and the 3-throw, but since they peak at the same time, you have to look in between and use your peripheral vision.
Step 4. Juggle a 531 once within a regular cascade. Note how throw 5 needs to be much higher than throw 3.
Step 5. Now you can juggle 531 continuously.
Variant. Siteswap 531 can be combined with others, for instance, making 53142 tennis.