I read this in the Mook ages ago but never quite figured out how to get this to work until today. Mai can do a j.D or j.B and then wall jump afterwards. The trick is to land the j.D or j.B on top of a cornered opponent's head (EDIT: It says j.CD as well). So essentially you hit them (blocked), your foots still touches the wall and you bounce off like normal and you can still cancel into her air dive if you want. Remember the hit needs to be on top of their head so you can touch the back wall (so deep hits won't work). The Mook describes how if the opponent see you "mis-time" a deep attack they'll try to punish with a s.C or whatever, by that time you've jump off the wall and started an air dive back at him (plenty of time to confirm) to punish his s.C.
Small tidbit, d.B x2, s.A / s.B, BC (Far C), hcf D works but sometimes the Far C misses so it's safer to do d.B, s.A, BC (s.C), into whatever or d.B x2, s.A, BC (auto dash), s.C...