I am really struggling to learn how to use these speedlites. One problem is that they are coy about having a low battery. The indications are arcane and seemingly undocumented.
I only have two, so one is on camera all the time. I did this moving the slave three times. Once to the right front. Once a bit above. Once behind for a bright back light. All three were diffused.
Got blown highlights on the one from the right. On the face maybe that is ok, but on the clothing it is unfortunate, a big white featureless slash...