Offer your best players for their rubbish ones
Its the same in our mini league, guess the only way is to keep pestering? Target the more unbalanced teams. If they have an abundance of attacking players then they're more likely to release a striker in return for a decent defender. Alternatively target someone who's squad is made up primarily of one Prem club - either offer some flexibility or complete a block eg Pompey defence? Once the game is underway you can also target specific results tables eg: Successful passes.
Are you in a public league or with people you know? How active are they at managing their squads?
Perhaps the most likely way to stimulate transfer activity is to propose double transfers where both parties get one player they really want plus one other. If you don't ask, you'll never know
