They are not easy for the chicken to get off, but they are very easy for you to get off. Just peel them apart the they come off.
The chicken will get used to eating and drinking within the first day. What these things do is stop the bird from being able to look straight ahead or in front of them. They can look down, to the side and up. So since they can not look forward, they can not aim will enough to pluck feathers, peck at combs, faces or bite head on. They learn quick that it is useless to bother the others if they are unable to aim their beaks in this manner.
I only use these for extreme birds. I would rather not use them, but if a chicken is endangering the others or me, and I do not want to rehome the bird, or eat it, LOL, then the I use the peeper method. You have to leave them on for a month or so and that seems to readjust the birds attitude, however if the bird you are using them on has a strong attitude, they will probably need to have them put on a few times a year. I have had some chickens only need them one time.