I never used medicated feeds...really no need. And there is especially no need when you feed FF and expose the chicks to low levels of coccidia that may be in your soils/coop/run. Since I keep things simple at my place, whatever flock takes priority in feed, that is what I feed the most of and I mix it right into the whole flock's bucket. So, when I have chicks, the laying flock get fatter because they are chowing down on 18% protein chick starter, for the most part, along with some of their regular laying mash. The chick starter is just a nod towards having feed particles small enough for chicks to fit into their mouths...you'd be surprised at just how big of pieces they can eat, though.
The chicks get mostly chick starter the first few weeks with a little layer ration mixed in but gradually, as the chick starter runs out, they get transitioned over to layer. Yes, I know everyone says not to feed chicks layer ration...I've even fed chicks straight layer ration from day one before when I didn't feel like buying chick starter. That group of chicks turned out to be the Gnarly Bunch, two of which I still have in my laying flock at 6 yrs of age.
It's all a matter of preference with no real wrong or right, but medicated starter will not insure your chicks do not get coccidiosis...there are many posts on this forum where chicks fed MS still got coccidiosis.
Anyhoo...I don't mix separate buckets, all feed is dumped into the same bucket and everyone gets what everyone else is getting. It works for me and works well, so I just keep doing it.