if the objective is development or grown players team, you just pick them a tutor,. you can read a lot of article about that in this forum.... another best option is loan them out...in u18 or reserve they dont gain any competitive matches ,..
i found that loan out them to playable league will force them to gain their potential abilities more faster rather than you hold them up. It's also related to training ground,...if your team has good training ground, they might consider to stay, so loan them out to a club that has good training facilities and definitely a team that need his position which has more playing percentage.. , e.g if a serie B club has only 3 strikers and one striker is injured and playing formation 442 you might send your youngster in there...
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yeah italy does have reserve but there is no fixture for it,..it's useless to place them there..