Remember that lemon juice and water plus sunlight is a permanent treatment. The procedure can dry your hair, so use plenty of conditioner. When I am outside in the summer sun, I like to use a spray on/leave on conditioner that is really diluted, but can stay on. By using some tender treatment to your hair and doing a little planning ahead, you can maintain moisture quality in your hair. In your plan, you can have the lightening process go slowly instead of trying to get a new color in one day. One of the costs of kitchen beauty for your hair will be that speed is not one of the elements, so you will have a time cost if not money cost. Another gradual increase in the lemon juice would work okay, but I believe there is a balance point where the benefits are not justified by the extra acidic application of a stronger lemon juice formula. It is a good idea to start easy with only about 1 tablespoon of lemon juice per cup of water. This formula is better applied to hair that is already wet. If you want sun streaks, combing the mixture through specific strands of wet hair, while avoiding other strands will work toward the streaks.