How do I do the lemon juice hair treatment at home?

Someone told me that soaking your hair in lemon juice is the same treatment a salon gives you to strip your hair of build-up. I'm just wondering if this is true and if so, how do I go about doing this? How long do I leave the juice in my hair before washing it out and does it matter what type of shampoo I use to wash it out? My hair is already dry, would this treatment make it worse? I'm a natural blonde and over time, my hair gets a dingy look to it. I'm hoping this may be the 'cure' for that.