Yes, but it will be a long day. My recommendation is, prepare your henna ahead of time and freeze it - this actually makes the dye release more intense. When u r ready to use remove and thaw for 8 - 10ish hrs - take it out before going to work or bed. This way when you are ready to do your hair, all you have to worry about is application time (4+ hrs) for the henna and then the Amla, 2+ hrs prep & application time.
HTH