In addition to the previous comments that all makes sense, don't discount sunburn and flakiness just from a buildup of sweat, dirt and flyspray from when the horse rolls.
I have two horses that have thin tails. The tail dock is almost nekkid in the center on the one horse
I have to apply a thick coat of generic diaper rash cream every morning before turnout and every 3 or 4 days, completely wash the tail dock with MalAcetic shampoo which is an antifungal, all natural shampoo.
A third horse has such a thick mane that it lays over both sides of his neck and gathers dirt, sweat and fly spray to the point that I have to clean his neck every day as well.
While the baby oil is an excellent suggestion, I'm not sure I would want to use it in this high heat and humidity for fear of it burning if the horse is outside during the day.
I might be more inclined to use a light coating of the generic version of diaper rash cream and just rub it in the same as one would the baby oil.
I think I'd save the baby oil to use during cooler temps
Hope this helps.