Suggestions for Kage's BT P+K, K Combo?

For the best damage, crouch dash in and:

* (closed stance) - -
* (open stance) - - +

should work up to mid weights. The timing of the first is critical. If you do it right then the second will refloat.

If that's too difficult or for heavier characters, do either:

* back dash, (medium range version of the heavy down attack)
*
* +
* crouch dash in,
.. the list goes on.