Need guidance on zinc and copper supplements brands and coat spray

Hi!! I recently bought a black horse, and he has already bleached out in the three weeks I’ve had him. I keep reading that feeding them zinc and copper helps with the bleaching, but where do I find this? Should I be purchasing off of an equine website?

I found a supplement for dark horses on State Line Tack in the link below. Would that do the trick? Any guidance you can provide would be greatly appreciated.

https://www.statelinetack.com/item/select-the-best-dark-horse-nu-image/E003897/

I think it’s too late to use a fly sheet, but maybe I’ll try it next year when I have a blank slate. He tends to get his fly masks off quickly, so I’m not sure how the fly sheet would work. Baby horse problems!

My next question is about coat sprays. Is there something I can use daily to help repel dust? He's always covered in dust, no matter how much I curry or brush him. I live in CA, and it’s super dry and dusty right now. I've heard Showsheen isn't good for everyday use. Has anyone had any luck with other products?

Thanks!!