I usually spin 3 times or until the first block is made, then do one of the following:
WS b+1 - Low and some mid crushing. Catches opponents off guard as well - D/F 1,1,1 juggles, which I usually follow up with u/f 3+4, 1+2, f+3+4, or something else if they techroll/the flea would leave me in BT
U/F+3 - Destroys high attacks, jabs and grapples - very handy if WS b+1 is failing. And obviously it juggles. You're screwed if it's blocked, however.
Grapple - Provides a decent surprise
WS 1 - Appears to stop all jab attempts and is safeish on block. For if your opponent gets wise.
Does anyone know of a way to stop all 4 of these? I've never played someone who doesn't get messed up by at least one of them regardless of their counterattack against manji spin slaps, but I'm guessing the reason it's not used often against facing, standing opponents is because there are way of slaughtering Yoshi after the spins?