he`l train fast but you won`t need green packs, what i do is sign 3 star player like him if free transfer or for 1 token and train till new season so he`l still be 3 star ( ish ) for you and add skill point`s on first day of season then sell as level 1 will see as 4 star if you go to level 2 and just watch bidding war as you will get more money in bank to be able afford 5 star player for level 2
yes, that's a good plan or else power training. Meaning, almost every hour, training in 3 bars + green pack (and some reds for possible injury) for the rest of the days - and not use him in games.