Because it's available at my favorite feed store, I switch from medicated chick starter to non-medicated feed at 8 weeks - "grower/finisher" feed. Pretty much similar to FlockRaiser. I don't switch to layer feed at all, because I have so many different ages of chickens in the flock. I simply keep crushed oyster shell available free choice, in two locations: in an empty tuna tin nailed to a coop wall next to a feeder, and tossed out onto the ground in a specific spot in the yard (so the ducks can utilize it, too). Those that need it, take it. Those that don't, taste it but don't eat much.
It's too hard for me to try to segregate layers from "not yet laying" and keep the layers out of the grower/finisher feed or the youngsters out of the layer feed. This works for me. Originally, I left layer feed in the coop feeder where the layers roosted, and put the grower/finisher feed out for the pack o' youngsters. But the layers ate the grower/finisher and their eggs began to get softer shells. So I switched EVERYONE to the layer/finisher and added the free choice crushed oyster shell. Fixed the problem.
Dunno what others would say, but I'd put the golf balls out just so you don't forget to do so when one of 'em lays. And I do not believe the amprolium in the chick start is one of the medications you need to worry about encountering in eggs... And Sunny_Side_Up is absolutely correct about being unable to "make" hens lay earlier! (You don't want to do that, anyway.)