I've never dipped corals in hydrogen peroxide either, but I would personally just remove any algea from the plug and then put some hydrogen peroxide on the area where the algea was.
I do however dip every coral that goes into my tank in Bayer...or at least now I do. At first I was afraid that dipping corals in pesticide would be hard on the coral so I didn't dip all of my corals. Apparently however the Bayer dip isn't all that hard on corals, it only effects animals that have a central nervous system, which corals do not have. I've dipped everything from softies, lps, and sps in Bayer and have never had any issue with it. Just make sure you rinse the coral really good before placing it in the tank.
Thanks. I use HP for Zoa's all the time even to clean the plug, GSP too. I wasn't sure about the Duncan. What I did was get some on a toothbrush and just brushed around the frag plug not the coral itself. If seemed to be fine. I usually HP the Zoa's when I start getting algae hindering the growth. About once every 2 or 3 months and the same with GSP. Once when I did this with a new batch something went sizzling across the cup of HP.