From the 2 choices you are looking at i would say you will make more profit from the spray tanning,
its quick to do 30 mins tops so you are in and out and have left a happy client looking fab and healthy,
eyelash shaping is going to involve waxing so you have to warm your wax up on the way there or when you get there, it may spill in the car (god forbid)
not everyone who has there brows shaped need them tinting so if they only want the shape, by the time you have driven there and back this will have taken any profit you had made,
and you would have to do 5 brow shapes to make the same amount 1 spray tan would make you,
hth :hug: