agreed, don't dip the nonoffending areas. use dental procedure, use metal precision tools/rasps/tiny knife to debride the algae off the septal ridges/areas without breaking them off, then at the end rinse those areas in sw to dislodge all bits.
then use q tip or other creative spot deliveries to apply peroxide to the cleaned areas then a quick rinse in sw after, its amazing how much dentistry translates into substrate management in reefs Ive found. if the areas are too fragile to rasp then spot apply the algae outside of the tank in some creative way/rinse off it'll kill the algae. Ive accidentally spilled 35% on my brain coral before/didn't bleach it as I rinsed quick for safety but I wouldn't dip flesh areas on purpose