RENO:
You need to charge the battery at high equalization voltage, in this case, around 3 Volt/cell with careful attention at the current to determine when it starts to drop and in that moment reduce the charge equalizing voltage to 2.6 volt/cell.
Depending on the sulphation level, the current may start low then after some hours to increase then it comes down a bit, that is when you need to lower the equalizing voltage to 2.6 observing the current behavior for flatness and possibly incrementing which should limited to 0.1 battery amp-hour limit -- so if the battery is 50 amp-hour limit the current to 5 amps.
Stop charging if temperature rises to 110 + degrees.
load the battery at not more than 0.1 amp hour and stop loading at 1.85 volt/cell and repeat the cycle may up to 5 times.
Nando