One of Sho's air specials, Metsuga, has a height restriction which limits it's usage in both combos and pressure. platefork gives a tutorial on how to bypass that by kara cancelling from C or D air Kousoku Idou. Check out the video below to see how to do the kara cancel as well as the various ways it can be applied.
It is not necessary to get black balls to enhance BRO. Regular balls can enhance it. The fastest way for that is just set then BRO.
If you want the fastest way to get a black ball:
Set > CR or SA
QV > CR or SA
Holding 2 ball then releasing is easier to charge but slightly slower
YRCing can give a lot of black ball possibilities
But because you want black ball into BRO. I'll say just a regular set or QV then CR or SA
However, the opponents pressure is situational and matchup dependent. You don't need to directly make a sequence. You can move or wait then complete