Praziquantel will kill gill flukes without any of that other stuff.If this were gill flukes this may be controlled with Masoten (organophosphate, not legal for food fish), praziquantel (2ppm for 3 days), formalin, potassium permanganate, and hydrogen peroxide (10 mg/L).
Organophosphates are extremely dangerous to all living things and should never be used. In addition to being harmful, most organophosphates no longer kill many fish parasites due to excessive use and misuse by various fish farms over the last 50 years.
------------------------
Gill flukes is not the main issue here. The guppy looks like it has gill flukes in addition to wounds/ sores and excess mucous. The excess mucous is the big issue and finding out the cause of this should be the first line of investigation.
------------------------
We don't have Flubendazole in Australia but a lot of people on the US forums used it with pretty good success. It treats a wider range or intestinal worms but also kills most invertebrates in the tank.Do you have any knowledge on Flubendazole?
The reason I like Praziquantel for tapeworm and gill flukes, and Levamisole for thread/ round worms, is because they are safe for fish and have no long term side effects.