Paul Carter put up a nice post on improving your squat.
5 Squatting Programs That Work
This isn't a technique post, it's purely programming. How many reps and sets do you do to improve your squat?
The 20-rep squats and 10 x 10 squats seem utterly brutal. I've done 20-rep trap bar deadlifts and 5 x 10 trap bar deadlifts and they were both rough. It can't be much easier with a heavy bar on your back. Just remember to stay tight and get low.