Hello Mgbchuck,
sometimes on my Clavinova and also on my Genos I have experienced the same problem volume on a part of the accompaniment, where the sound is weak, and even increasing the volume does not solve the problem.
After after several and various attempts, I discovered two ways to increase the volume:
-this option is valid for any part/any sound: you can increase the volume (of course over the 127 volume value) by selecting as the insert effect, Compressor: it gives you an unbelievable additional range of volume, by tweaking on the output parameter of the compressor effect;
-this second option works with drum/percussion part only (that are the only parts of the accompaniment that Yamaha allows us to edit): go in Style Creator/Edit, and modify the level of the instruments (in your case: brushes) whose volume you want to raise. This method is effective if the level of the brushes is not to near to 127.
Often, if I change the voice for the Pad part, the new voice can be weak, even if I set the part volume at 127. If I assign the Compressor effect, I get an huge amount of extra volume (normally at 40-50% of Compressor out level, I get a very high volume.
I'm sure there could be other methods. But I'm quite satisfied with the above ones, as I solved all problems of volume on a specific part/sound that I faced with.
Hope this can help. But I'm curious about alternative/additional methods.
Ciao,
Angelo