It is not always possible to positively identify dermatophyte infections on physical examination and Wood' lamp examination alone. Only approximately 50% of Microsporum canis infections will fluoresce under UV light. Positive identification is best done via implantation in culture media and this is easily done in a clinic setting - the downside is the 7-14 day wait for a result, so treatment is usually started on a presumptive basis and modified once results are actually known. Direct microscopy using KOH is highly user dependent and therefore considered less reliable.
Wash the dog in Malaseb or if it is sensitive then try Nizoral anti-fungal shampoo.
Most importantly hygiene. Don't let him wonder around everywhere, wash bedding and dog beds, it's probably too late now but you should wear gloves when handling/treating.
It will take many many weeks.
Soak the bedding in bleach,wash with canestane in wash liquid, Dry in the sun.
Canestane wash is expensive but good.
There will be lots of different opinions on how to clean and treat. These are just a couple more.