I don't really understand post moisture sprays, mainly since like Jenuinetan said, it washes off after the first shower. I would look into South Seas retail line. They have a lotion and a butter that are great and formulated especially for sunless clients. However, regardless of the
solution , the higher the DHA the drier the skin will/can be following their session. Reminding your clients to drink plenty of water (to keep the skin hydrated from the inside out) could be another tip for them? Good luck!