Regarding contaminating the powder with lube:
If you stood all your brass up in a loading block,and sprayed from overhead,you would have the full area of the neck I.D receiving lube.Probably not best practice,but nobody stands the brass up in a loading block and sprays down from overhead.
If the brass is laying on its side,there is theoretically zero area of open neck exposed to the spray if it comes from directly overhead. Kind of like you can enjoy standing in the doorway of a barn watching the rain and stay dry if the wind isn't blowing.
If we apply that idea to spraying the lube on,if the brass is fairly spread out,like in a cake pan ,its mostly horizontal.There is not much open neck target area to hit. We are not flooding the brass,we mist it.Then,we shake it around to transfer the lube,like tossing a salad.
The point: If you do it right you don't have to worry.And the slight amount that might crawl into some of the necks is not a runny pool of oil.It gets wiped by the expander plug. IMO,a little of that is actually a good thing.