Also when you speak to the board try using the "If you don't grant this we'll be left behind by our rivals" reply. It works more often than many of the others in my experience.
As for successful loans, sadly the best way is to indeed find a feeder team.
Also try offering them for free as to the fee, along with 50% or even zero for wages. As a bonus, if you offer them for free you can recall them at any time to fill holes in the first team. Use the "offer to club" as often as once every day if you have to. But be wary, it's not advised to loan players out if the team you plan to loan them to gives you a reply less than "We think they will become a valuable member of the first team." Otherwise they'll probably feature in only a match or two all season, and in that case it would be better to have them playing in your reserves or even riding the bench of the first team.
Play them as much as possible in pre-season, even booking games entirely for youth players, and that will help them develop. You might also make huge profits if you book the right teams. You might just try getting them into the first team for 5 - 7 games a season if you can. It really works wonders if you get their morale up.