Yeah, I use them every season.
To meet % promises, I move their Stamina Effectiveness to 60% when I play Sim teams and start them so they play nearly 100% of the snaps. That gives me the ability to reduce their PT against human opponents.
For starting spots, I move them into a starting position on the depth chart for one half or the other at 95% effectiveness.
I only use one formation on both offense and defense and rarely even use variants of that formation. If you use different formations you're going to want to make sure they get at least 55-60% of the plays in the half that they start.
*** Fun Fact #1: you can promise PT and still redshirt guys, as long they don't have a promised start.
*** Fun Fact #2: a DNP (so 0% playing time) doesn't impact a player's total % of plays for the season (Game 1 -100%, Game 2 - 0% will be 100%, etc.). I never use this trick because I usually play all 47 guys. Even the 3rd string QB usually gets a few plays