If you're willing to eat a Mythril to win, you could always purposely sacrifice your first run. Use your first run to live as long as possible and build up SB's (Don't use any / use as few as possible). They carry over if you Mythril/Gem a retry, so you could start the second try with ~2 SB gauges already built up.
It's a last ditch thing really but it's always an option if you don't mind eating 1 Mythril and your synergy is shitty. Not sure if SB carrying over to second attempts is common knowledge as I never see it suggested (I know winning first try is the ideal solution...)
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