When using the cool tool you do not need a lot of force, you just have to make sure you are pushing where it is necessary. If the door is not closing and you are having to apply a great amount of force, then there is something else that is not allowing it to close, wether that be your not pushing in the right place for a bend, you are missing torque that may need to be applied, or there is wire-tie or powerchain in the door, etc. Too much force or squeezing too hard on the bracket door can break the bracket so if you are having trouble you can always ask your team lead for assistance.