I've usually used caustic soda diluted in water @ about 2 teaspoons to 500mls of water.
Be aware! wear protective clothing and gloves, hat/goggles if overhead, and, consider a face mask there are minimal fumes even at this dilution and it's corosive in nature. Apply liberally with a well wetted sponge and protect surrounding areas especially the floor and surrounding metal/paintwork.
Treat as you would any other paintstripper, leave to work for 15-20 mins before attepting any removal, look for blistering/slime. re-apply as required. the 'mixture' keeps indefinately in a coffee jar or similar.
After successful stripping, wash wood with plenty of warm water or consider using white spirit to ensure the grain doesn't rise or split. leave to dry, consider what coating to use! :-)