Mass Attack concepts and principles are also (of course) present in Long Form 4. One of the primary mass attack principles contained in Long Form 4 is the ability to generate power directed in opposite directions simultaneously. This teaches you how to effectively use transitions to generate the power needed to stop an attack.
Another principle in defending against multiple attackers is in the positional blockade created by dropping your attacker and then using that attacker as a building block in a wall around yourself. Take notice of the locations of your attackers' bodies once they have been dropped, you will soon see a wall being built around yourself. This wall reduces the paths of attack your other attackers can take. Think of the two-man technique The Ram and the Eagle. As you finishing the Flashing Mace section, you have an attacker you can position between you and the next attacker. After the Five Swords section, you are again hiding behind the second attacker in case the first one returns.
The first part of the form concentrates on attacks from the front 180° between 9:00 and 3:00. The middle part of the form has you moving back and forth between the back half and the front half and horizontally between 9:00 and 3:00. The last part of the form focuses on the 180° in back of you between 3:00 and 9:00. When you are finished you will have attackers laying on top of each other in a complete circle around you.
Finally, as you build this wall of bodies around you on the ground, the formís otherwise innocuous (and sometimes difficult) foot maneuvers become nasty movements that can crush bones and further knock attackers around. Try doing the second Destructive Kneel while your original attacker is still there; you will continue to hit them as you proceed to focus on your primary attacker. With other methods of footwork, you are often catching the fallen attackerís arm between your feet when you execute a rear crossover and then spinning out, breaking the arm in the process. Many of the twists and turns can be thought of as breaks to arms, legs, and necks from attackers that you have downed in the previous segment. (Think of what you do to your fallen attackers with the twists and steps in Destructive Kneel or Gathering Clouds-- there are arm breaks and neck breaks as well as stomps to kidneys and ankles and other vulnerable body parts.) The idea here is to simply play with this idea. Get a bunch of attackers and go through the first few segments of the form. If you have enough people, keep them laying around as you maneuver through the various attacks to see how much damage your feet are causing as well as strikes that follow through against your attacker and catch the fallen previous opponents.
Other areas to look at would be in isolations. Of course, the idea of an isolation is to merely show concepts than can be used for category completion or to show you previews of what is to come. That is how forms were designed, but when you place attackers in front and behind you (and maybe at your flank even) as you hit the isolation following Protecting Fans, it can be seen as a variety of weapons against multiple attackers.