After you remove a scab and pack it with the triple antibiotic and bandage for a couple days, the scab area should be healed over enough that you could let your duck bathe in clean water. Then you could re-bandage if needed. I don't like to let me ducks go more than 2-3 days without swimming...
Pekins are especially prone as they are heavy weight birds. Maybe you want to post a picture of the bumble and ask for advice. If it's a large one you probably need to pull the scab after soaking in epsom salts. I also have pekins and have had two with bumbles, which have been larger than the...
Well it was my welsh harlequin, who is super light weight, and it was a tiny bumble, caught very early. That said, it worked great - I never soaked, picked, or bandaged and it just went away after a few weeks.
@Ratchnick - I would love more details on your method - what antiseptic, and did you then try to keep the bird out of the water for a time, or just the five minutes?