The frontline pump is the right chemical but a really awkward and inefficient way to treat mites. However it is the only chemical licences for treatment of mange and therefore the vet HAS to try that first due to cascade laws.
The only two things I've found effective for mites are Dectomax injection or Fipronel (Frontline) spot on. The first is the best but needs to be admistered by a vet. The second can be easily bought online without a prescription. Front line brand annoyingly comes in packs of 3 but other brands (Effipro for example) comes in packs of 4). I use a large dog pipette per leg every 3 months, which keeps the mites at bay. You'll never kill them completely, only manage them
Has regular Dectomax but don't seem to work. have used Dectomax, frontline and shampooed with dermoline as a 3 pronged attack, will try spot on stuff next !
Seleen General Dermatitis Shampoo for dogs will probably work. It is an AVM-GSL medicine so doesn't need a prescription. There was a paper published a number of years back showing its efficacy to treat feather mites in horses.