For us to help you accurately, please provide us with this information:
1. Natural level of the client
2. Desired level and tone of both hi/lowlites
3. Product used
I also want to say that I prefer to use foils for this sort of process. The reason is that I have more control over the placement and speed of processing of the hi/lowlights. I alternate the foils with lightener and color, and formulate according to what I see. I might need a higher volume of developer for the blond, and sometimes lower, depending on what's needed to lighten, or catch up to the color, or determine whether a permanent (oxidative) color is needed, or a demi. For example, I might use only 10 vol. for the hi, and 30 vol. of permanent color, or 30 vol. for the high, and a demi for the low and process for 20 mins Maybe heating the foils with the lightener with a blowdryer if needed). Also keep in mind that lifting through natural color, and artificial color are two different things, and are needed to formulate and process accordingly.