To be honest I wash immediately after handling any snake. Even those I assume to be 100% healthy. Just because I do not wish to expose otherwise healthy animals to pathogens that may come from an asymptomatic animal.
Washing before and after handling any animal in QT is a must.
Thoroughly disinfecting any shared implements before and after use is another must. Although I often find it easier to keep an extra set of hemostats or tongs solely for feeding a new animal in QT etc.
Animals in QT should not be kept near other animals in your collection. If you have limited space and a new animal is introduced to your QT area the QT clock starts over for every animal in QT.