@Amanite Ito.
1) Afaik, saving SP won't help you in cup draw because game's engine counts unsigned skill points. That is reason why some managers use quite unusual and expensive strategy for cup: they sell their best players before new season starts and buy some free agents or receive them by auto add (when number of player in team is equall or less than 14, team receives few retiring 3* players. This way team's quallity significantly falls down.

2) This strategy is good, but even better if you can find some reliable and wealthy buyers. Open auction's tab, find 3* players (all expect FA's!) and then watch auctions for some valuable players. After end of auctions, add bidders which spend a lot of tokens on auctions. Send them frendship request and maybe message if they want to buy players from your team. When they add you as a friend, they can buy any of your players, but actually they will be able to buy only your 3* or weaker players since they are on lower league level.
Also you can add as friends managers which already bought your ex players.