Personally I tell my clients to shave or wax at least 24 hours before their spray tan appointment. However, it is possible to shave afterwards, but not within the first day.
Most of my clients shave around three days after having the spray tan. I do warn them that this lightens their tan as it has an exfoliating effect, but it shouldn't look patchy.
I myself shave a few days after a spray tan and it does lighten it, but never looks patchy.
Do not wax afterwards though unless you want to remove your tan completely lol!
xx