As you know, attacks come fast and furious so there is little time to perform traditional blocking techniques. In a fight, you keep your guard up, go with the flow, maybe block if the opponent is using single technique attacks or the attacks are slow, and take advantage of any openings the attacker presents to attack and finish the fight.
It is practically impossible to fight more than one opponent, except in preplanned demonstrations. Think about the difficulty in sparring one opponent. Now think about having to also spar another opponent directly behind you who attacks simultaneity with the first opponent (real attackers will not take turns attacking). When concentrating on one opponent, you have no idea as to what is happening behind you. The best you can do try to maneuver so both opponents are in view, and then try to eliminate one opponent with a deadly attack so you only have one opponent to fight.
If one persons attacks, you have a choice as to whether to stop, injure, or kill the person. Which option you choose depends on the intent and actions of the attacker. If two persons attack, at the first opportunity you must eliminate one of the attackers. The one you choose may not have intended to seriously harm you, but that's too bad. One opponent must be eliminated quickly and it will usually be the weakest one.