Word of advice...
Set fighters to R8 and 0 priority. You don't want people commanding them. There's a glitch that causes fighter pilots to gain MASSIVE amounts of Fighter Combat Bonus, which leads to promotion scores being completely askew (e.g. 100,000 promotion score at Commander rank).
I presently have a Rear Admiral who's only in his 30s, and has been there since he was 25. He piloted a fighter for just a couple years. He had no talent what so ever, save for fighter combat, for some time. He's finally getting somewhere.
Now, technically, if you really need someone to be promoted fast, you could assign them to a fighter.