With a Scotch Brite pad, you will rough up the resin on a Big Bang. Not much except Diamond pads are able to change the particles, so don't worry about that. 400 grit? I assume you mean the maroon pad. It is considered to be about 320 grit US. The green one is considered to be about 600 grit US.
Meanwhile the Big Bang, if you have less than medium revs, is not the ball, from several aspects, for heavy oil. The core on that one usually helps with some length, but you've countered that with a fairly rough surface.
In any case, I'd recommend several other of their particles for a better look on medium-heavy to heavy oil: the new Dynamic Power is fairly inexpensive as Lanemasters balls go. The World Class particle (solid blue) is an earlier rolling variant of the Big Bang. The Terminator & Black Pearl particle will also help you handle heavier oil, once you remove their shine.
By the way, redrilling the BB for an early roll, like a rev leverage drilling, would also help a lot.
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"None are so blind as those who will not see."