I just take mine out of the space/nest where they are broody and then lock them out the pen for three or four days. I have done it with a few Bantam Cochins lately and it has worked each time. It still takes them a while after that to start laying agian.
Having broody hens will definity cut down on your egg production. Not only will the broodies not lay but they will fight with the laying hens to keep them away from what they see as their nest. Anything that upsets your flock will cut back on their laying and may even cause them to go into a molt. Seperate the broodies and put them in a pen with no eggs. You can put them together as none of them will be laying. In about 2 weeks you can put them back with the flock if they show no signs of broodiness. Be ready for some fights to breakout when you reintroduce them to the flock. That is normal until they work out the pecking order.