I took them up to 56-57 volts yesterday with the windturbine at about 15 amps, I noticed tiny bubbles starting to accumulate in some of the cells, Is this the bubbling I should be looking for?
Yes. When the cells are fully charged and you drive extra current through them to continue charging the cells that are low, the fully charged ones electrolyze some water and bubble off hydrogen and oxygen. This is what you want to see.
And how long or much do you do this for? How can you tell if they are equalized as much as they are gonna equalize?
I'd say go until they're ALL bubbling (or the voltage is high enough to indicate that all the cells are at the fully-overchaged level). But stop if you've gone long enough that the charging amphours you've driven in is enough to fully charge a completely empty battery - like maybe 110 to 120% of the amphour rating. (Somebody more familiar with this can correct me if I'm off, please.)
and what are the dangers?.It is well ventilated and no people around.
That takes care of injury due to explosion from the gasses released. You should make sure your cells have enough water before you start, so you don't "boil them down" (electrolyze too much water) and expose the plates during the process, and make sure they're full when you're done, too. Running a cell nearly dry can explode things when the bubbles fully cover the submerged part of the plate and cause a spark in the midst of that explosive mixture. Overheating if you do it too fast, damaging the cells. Damage to your electronics on the load side if it's not rated for the higher voltages involved when applying an equalizing charge, or before the surface charge is removed and the battery voltage is down to the normal operating range by ten minutes or so of moderate load on the battery.
I've probably missed something.
Wear safety goggles and have a neutralizing solution spray bottle handy when examining the cells for bubbles, in case they spit at you or pick that moment to blow up and spray you with electrolyte.
All this is very low probability if you made sure your cells were watered before you started, have good venting and no sparks, and don't drive TOO much current in or drive it for too long.