The article mentioned that the Skyhawks were dramatically lightened by stripping out hard points and weapons to improve maneuverability. Did these planes sport any other custom modifications?
This photograph gives some context.
There were two main factors loading things in favour of the instructors at Top Gun.
Firstly they were the instructors. The perceived problem Top Gun was designed to address was a feeling that US pilots had become de-skilled in dogfighting since Korea and needed re-training. Their Phantoms were designed to give the technological edge and avoid dogfights by shooting down opponents "beyond visual range" (BVR) before fights could even start. For various reasons BVR wasn't working out so well and dogfights were occurring. In a close-in dogfight experience and confidence are huge factors counterbalancing (within limits) any technical advantage one plane has over another. So easy, early wins for the instructors would be expected.
Secondly the Aggressor aircraft were chosen to replicate the advantages that the enemy had. The A-4 was supposed to be an analogue for the MiG-17. It was designed as a light bomber so when stripped down and not hauling nearly its own weight in bombs it turned out to have a low wing loading with good acceleration and excellent low speed handling. Medium to low-speed is where dogfights happen and until Phantoms' wings were modified in 1972 to give acceptable low speed handling they were very poor in this regime. Their high top speed meant that they could disengage if they were losing, but at lower speeds they couldn't easily manoeuvre to stay in the fight and win. So in a close-in fight the A-4s were small, agile targets and the Phantoms were large, lumbering targets.
F-5Es played a similar role to the A-4s, but were analogues for MiG-21s (NATO reporting name Fishbed), so the balance of speed and manoeuvrability was different, but still heavily against the F-4s.
To get back to the "various reasons BVR wasn't working out so well" I referred to, Phantoms were built large to carry the large radars, large missiles and large fuel load required to fly long distances fast and then to kill enemy bombers flying straight and level from beyond visual range. They were very good designs for this role, but they were rubbish dogfighters.
In Vietnam they were not supposed to kill BVR as rules of engagement said they had to get a visual identification of their targets. This put their rather unreliable main Sparrow armament out of use as it was long-range only. The Phantoms initially had no guns so they were reliant on their short-range Sidewinder missiles. Unfortunately dogfights were at too close a range for these early Sidewinder variants and they struggled to lock onto their fast moving targets. The MiGs were flying close to home, didn't require huge range and could afford to be small, light and agile compared to the Phantoms. They had good gun systems and could easily get behind the Phantoms, which were struggling in their opponents' zone of advantage. Results were disappointing if you were American, encouraging if you were Vietnamese. This situation was replicated at Top Gun so that pilots could learn how to deal with it.
So the answer to your question isn't so much that the Aggressor squadrons were using special tactics. Essentially they were using traditional tactics updated for jet aircraft. It was the immaturity of the new tactics and technology that was putting US pilots back into an old situation.
Well, if they were going against F-4 Phantoms, one of the problems faced by the F-4 pilots was something called "adverse yaw". So, whereas normally in dogfighting you try to pull tighter high-g maneuvers against your opponent in order to get into better position, the F-4 experienced serious adverse yaw at high speeds and high g turns. When a plane rolls to a turn, the ailerons on a wing act opposite each other and you produce a motion thusly, where the up-going aileron produces significantly more drag than the down-going aileron, and so the force pushes the wing down. In adverse yaw, the down-going aileron actually produces more lift than the up-going aileron, and so the plane rolls in the opposite direction as intended, as well as experiencing a yaw in said direction. This often caused stalls and flameouts, so high G, fast turns were to be avoided in the F-4
