K.I.S.S. is an acronym for systems or procedures in business : Keep It Simple, Stupid. Or, like
@Brute 23 said " Keep It Super Simple" ( I kinda like his better, actually). Since you have water outside of the pens too, then put your mineral/salt feeders in the pen. You want to have it to where they have to go in there every day to get something.... be it water, food, salt...whatever, thus having to pass under the dusters, oilers, etc. With just 8 head, you can get feed-through fly-control minerals, too. If you get soil samples before you fertilize your pastures every year (and you should), it will show any mineral deficiencies , and can be added into your fertilizer mix, too. IMO, this is very important. Just applying any kind of standard mix fertilizer is a waste of money.....like being sick, and walking into a pharmacy, and grabbing the first bottle of medicine you see. If it isn't what you need, it won't do you any good, and could actually cause harm. Honestly, I think you'd have to
try to make a mistake with how you are doing things now. You got this!