Since we are just doing a test rock and evaluating in three days--if you can believe it you don't even have to rinse it, you can just put it back in tank. The only animal we keep that would stress from that is a lysmata cleaner shrimp, if you don't have one then no form of rinse/no rinse or pour/spray will affect anything badly
Many people like to spray as long as the algae gets a good zap it should work nicely. If a test rock pans out clean and then we do the rest same way and zap all this out I'll link you up to the big peroxide threads as before and afters help others head off a takeover. For me personally I'd opt for no rinse over using freshwater, and for any type of saltwater if a rinse was wanted. Peroxide will lighten out the coralline in treated areas but it will come back and the algae will die. Whether one treatment permanently cures the tank doesn't matter, it's the fresh start that allows any number of algae prevention modes to hopefully take over. If they don't work, zap again.
This method is literally a chemical cheat to start fresh with the goal of a more legitimate method taking over if you can find one that works as well lol
The best part of the threads is the hundreds of tanks not losing anything by trying. If you have an algae that won't respond , the test rock will show. The zoanthids would tolerate any form of peroxide dosing you might try, #1 of toughest corals to peroxide but the first test is for no coral contact, just algae watching
It wouldn't hurt a thing to do the whole rock structure at once, but people like the test rock better to save work if the algae happens to not respond.