Two core principles behind mastitis control are to minimise the number of bacteria on teat skin and to maximise & maintain teat end health.
Whilst pre-milking teat preparation is not routinely used in most Australian herds, there is good evidence that targeted use can be of significant benefit.
In situations where there is excessive exposure of teats to mud and/or faecal material, the introduction of a pre-milking wash & dry routine can significantly reduce the number of bacteria on the teat surface and hence the risk of mastitis.
Removal of this contamination also allows the teat disinfectant to get to the skin, maximising the chances of both killing bacteria and getting emollient to the skin surface to improve teat skin health.
Remember that "gold" standard is to have cups going onto clean, dry teats after the cow has had a milk let-down.