I use bent wire taped to a small torch but I prefer to use a magnetic screw driver that holds against the side of the link allowing it to drop on the hook.
I find the bent wire hook often gets caught in the various pipe work on rolling stock.
The hooks on Heljan couplings are awful. The hook almost closes the gap preventing Dapol and parkside stock coupling up,hence why I snipped the tip off mine allowing a wider gap.
Paul