Developing and maintaining technique is something that needs to be practiced by all athlete, regardless of the sport.
However, Powerlifters don't employ the right method for optimizing technique. Powerlifter tend to develop strength by using the lift for the strength training exercise.
Research and empirical data show that technique changes with each repetition as the muscle fatigue.
Thus, the last one to two reps in a competition Squat, Bench Press and Deadlift you develop poor technique.
The objective in a rep where you grind it out shifts from technique to "Get it up no matter how you can."
Developing Good Technique
The most effective method of developing good technique is by performing single repetition with load of 85% plus of your 1 Repetition Max under the following conditions.
1) Technique Training needs to be performed first in your program when you are fresh.
2) The number of set of single is determined by fatigue. Once fatigue appears, terminate you Technique Training. Continuing in a fatigued state lead to and reinforces poor technique.
400 lb Squat Example
If your 1 Repetition Max is 400 lbs, performing single reps for set of 340 lbs (400 lbs X 85%)
Olympic Lifter utilize the method prescribed above They don' preform set of 5 to 10 reps of Olympic Clean and Jerks or Snatches.
Pole Vaulter don't vault for reps, Baseball Player don't bat for reps, Quarterbacks don't throw for reps, etc. They develop their skill by essentially preforming one rep at at time: vaulting once, batting the ball once, throwing the football once.
Building Strength For The Powerlifts
Auxiliary Exercise that are similar in nature to each lift are used to develop strength.
As per your example...
- Close grip bench press instead of competition grip, and incline close grip as accessory.
- High bar squat, with beltless pause squat as accessory.
- Deficit snatch grip deadlift, with no accessory deadlifts.
Research show one the biggest key to increasing strength as well as hypertrophy is to constantly rotate Auxiliary Exercises.
As the research article above cites, "CIVE (Constant Intensity-Varied Exercise) is more efficient to produce strength gains...as long as the training intensity reaches an alleged threshold
This research data reinforces...
Simmons Westside Training Protocol
This method constantly employs Auxiliary Exercises to develop strength for the Powerlifts.
Auxiliary Exercises are constantly rotated.
Dr Tom McLaughlin's Research
McLaughlin (former Powerlifter/PhD Exercise Biomechanics) research came out about the same time as Simmons' Westside Protocol, circa 1980.
McLaughlin's found technique was best developed with single reps with 85% of 1 Repetition Max Technique Training.
Auxiliary Exercise were used to develop strength for the Powerlifts.
Simmons Conjugate Training Protocol has demonstrated that training Limit Strength (1 Repetition Max), Power and Hypertrophy is one of the keys to increasing the Powerlifts.
Dr Michael Zourdos' Research
Zourdos' (Powerlifter) research found Conjugate Training which incorporates Limit Strength, Power and Hypertrophy (as Simmons found) demonstrated greater increases in strength.