Drain/equalize them to remove all residual charge.
Charge them at 330 mah (or as close to C/10, where C=mah of batteries, which in this case is 3300) for 14 to 16 hours.
Discharge mildly (say 5 to 10 amps) to 5.4v (.9v/cell) then equalize them again.
If you have time, do another cycle of that 14 to 16 hours.
For the first few "fast" charges, try charging at 1 amp first. Then discharge and equalize again as above.
Sometimes it takes a few cycles to "wake them up". After about 3 to 5 cycles, they should be ready to take in those 5 amp charges again.