For a Li-ion /Li-Po thats deep discharged, all you need is 4.2V ideally (5V will also do)
The initial charging picked by the BMS will be at extremely low current so you do not need a high current power supply at all.
Those old metal connector batteries could be revived simply by holding wires against the metal prongs hooked to 3 AA batteries in series .
The sealed ones typically come with a JST connector so you will either need to peel the plastic or use thin prongs to make contact with the JST connectors.
if you can manage to carefully align and push a few strands of a regular copper wire into the connector , that will also do
A 1-2 min trickle charger this way should be hopefully enough to get the battery ready to accept charge through the phone board - unless the battery is well and truly dead.
You do not need any tools for this tbh - just a bit of patience