After putting a lot of things from theory into practice, we increased a lot of sets/reps/and reduced rest time and moved on to goblet squats.
Goblet squats (heels elevated) + a dumbbell in order for his body to adapt to the external weight he had to move within getting down and standing back up. We started off light, to build up to 15kg.
So now we did a back squat (with the broomstick) and we added external load onto a Goblet squat, which meant: time to put the 2 together! 15kg meant we could introduce the barbell to his life. 🙂